source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-2044 | entomology, reptile
Title: Had there been a non-flying pterosaur? Since there are non-flying birds and secondary non-flying insects, it is reasonable to assume there were also non-flying pterosaurs. Well, according to this source there are no flightless bats, so it isn't an absolute that all flying clades have flightless members:
https://pterosaurheresies.wordpress.com/2011/07/21/meet-the-first-flightless-pterosaur-sos-2428/
Everyone knows about the various flightless birds: the penguin, the dodo, the ostrich… the list goes on. There are no flightless bats. And no one has ever discovered a flightless pterosaur… until now.
But the short answer to your question is: no confirmed flightless pterosaur fossil seems to have been discovered so far.
The longer answer is: from what I can tell no pterosaur has been found that was clearly flightless, but pterosaur flight isn't well-understood in the first place so there is debate as to how and whether some specimens could have flown. It seems to be the consensus so far that they did fly however (based on the lack of mention of flightlessness on the Wikipedia page, and the last paper I link to in this answer is fairly convincing).
As far as not finding flightless specimen, the above link claims to have found one but the source is not reputable and I found no confirmation of it elsewhere (Wikipedia confirms, and I'm usually all about Wikipedia but here the page has all the hallmarks of having been written by the same person who wrote the blog). The same author argues a large pterosaur is flightless here, but their arguments are quite poor compared to others made in the field and they seem again to be the only ones making them.
Here is a post from Tetrapod Zoology in 2008 imagining what a flightless pterosaur might be like, and also claiming none have been found:
The following is multiple choice question (with options) to answer.
The earliest vertebrates were jawless what? | [
"fish",
"mammals",
"dinosaurs",
"reptiles"
] | A | The earliest vertebrates were jawless fish. They evolved about 550 million years ago. They were probably similar to modern hagfish (see Table above ). The tree diagram in Figure below summarizes how vertebrates evolved from that time forward. |
SciQ | SciQ-2045 | water, solubility
Title: Does CO2 dissolve in water? First of all not a homework question, but one day it suddenly popped into my head while opening a bottle of soda and accidentally leaving a glass out for a while.
I get that $\ce{CO2}$ in water is not the same as Carbonic acid, however this also raises the question if $\ce{CO2}$ can combine with water (It does so in acid rain in the atmosphere(I would guess normal temperature and pressure)), then shouldn't dissolved $\ce{CO2}$ just form carbonic acid and hence become unusable for aquatic plants? And also if Carbonic acid does form in the atmosphere ( Again,I would guess normal temperature and pressure (feel free to correct me!)), why does the fizzing happen in soda bottles when opened in the first place, should Carbonic acid be stable at normal conditions?
Please do note that I talk about $\ce{CO2}$ dissolving under normal temperature and pressure
I feel like I'm missing something super basic and obvious here and I just can't put a finger on it.
Thanks in advance! I want to extend Maurice's comment:
The amount of $\ce{CO2}$ dissolved in water is proportional to the outer pressure. At $\pu{20 °C}$, 1 liter water dissolves about $\pu{1.7 g}$ $\ce{CO2}$ at normal pressure (1 atm). If the pressure is twice as large, the amount of dissolved $\ce{CO2}$ is twice as much, $\pu{3.4 g}$.
To talk about solubility of gases in liquids, we take the help of Henry's Law which states that:
The amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid.
Mathematically,
$$\pu{S_g=k_HP_g^\circ}$$
where $\pu{S_g}$ is the solubility of the gas, $\pu{k_H}$ is the Henry's law
constant which is different for different gases and $\pu{P_g^\circ}$ is the
partial pressure of the gas.
The following is multiple choice question (with options) to answer.
In which kind of water can less carbon dioxide dissolve? | [
"tap water",
"warm water",
"salt water",
"cool water"
] | B | If a solute is a gas, increasing the temperature decreases its solubility. For example, less carbon dioxide can dissolve in warm water than in cold water. |
SciQ | SciQ-2046 | neuroscience, neurophysiology, sensation, hearing, human-ear
Title: Why/how does exposure to noise cause cochlear hair-cell loss? I am trying to understand why listening to loud music - e.g. concerts or earphones at high volume damages hearing.
According to the National Institute on Deafness the cause is physical.
Most NIHL is caused by the damage and eventual death of these hair
cells. Unlike bird and amphibian hair cells, human hair cells don’t
grow back. They are gone for good.
But I don't understand why/how would noise - which should basically lead to higher amplitude waves in the basilar membrane, induce damage and death of these hair cells? There are a number of pathophysiological mechanisms that are thought to underlie noise-induced hearing loss:
Mechanical damage to the delicate cells and supporting structures of the organ of Corti;
Reduced blood flow to the inner ear;
Intense metabolic activity, which increases mitochondrial free radical formation.
Reactive oxygen species (ROS) are highly reactive. They are essential for mitochondrial function to generate energy. However, too many of them damage cellular lipids, proteins, and DNA, and upregulate apoptotic pathways. The observed impaired blood flow to the cochlea can enhance the toxic effects of ROS. Mechanical damage to the delicate hairs and membranes of the hair cells reduces their ability to converge acoustical energy into potential differences.
References
- Le Prell et al., Hear Res (2007); 226(1-2): 22–43
- Kurabvi et al., Hear Res (2017); 349: 129-37
The following is multiple choice question (with options) to answer.
The cochlea is a shell-like structure that is full of fluid and lined with nerve cells called what? | [
"brain cells",
"sperm cells",
"red cells",
"hair cells"
] | D | The stirrup passes the amplified sound waves to the inner ear through the oval window (see Figure above ). When the oval window vibrates, it causes the cochlea to vibrate as well. The cochlea is a shell-like structure that is full of fluid and lined with nerve cells called hair cells. Each hair cell has tiny hair-like projections, as you can see in Figure below . When the cochlea vibrates, it causes waves in the fluid inside. The waves bend the "hairs" on the hair cells, and this triggers electrical impulses. The electrical impulses travel to the brain through nerves. Only after the nerve impulses reach the brain do we hear the sound. |
SciQ | SciQ-2047 | bond, ions, ionic-compounds
Title: Why is the overall charge of an ionic compound zero?
My textbook simply says:
Since an ionic compound consists of equal number of positive and negative ions, the overall charge of an ionic compound is zero.
But why is the number of positive and negative ions equal?
Can’t an ionic compound can have an unequal number of negative and positive ions? Why or why not? Sodium needs to lose 1 Electron to attain stable electronic configuration and chlorine needs to gain 1 electron to stable electronic configuration.
In a big picture, the electron was transferred from sodium to chlorine in the same neutral crystal. No electron was supplied to the crystal from outside, it was already in the same system before and after the formation of NaCl.
If the system before formation of NaCl was neutral then it will be neutral even after the formation of NaCl crystal. That may be the reason.
The following is multiple choice question (with options) to answer.
What is an electrically neutral compound with positive and negative ions? | [
"neutralized molecule",
"isotope",
"correlated compound",
"ionic compound"
] | D | Most of the rocks and minerals that make up the Earth’s crust are composed of positive and negative ions held together by ionic bonding. An ionic compound is an electrically neutral compound consisting of positive and negative ions. You are very familiar with some ionic compounds such as sodium chloride (NaCl). A sodium chloride crystal consists of equal numbers of positive sodium ions (Na + ) and negative chloride ions (Cl − ). |
SciQ | SciQ-2048 | astrophysics, orbital-elements, celestial-mechanics
For the solar system, it is conventional to take the x-direction to be in the direction where the plane of the equator crosses the plane of the Earth's orbit around the sun. And the y-direction to be perpendicular to it, in the plane of the Earth's orbit (so by definition the Earth has zero inclination). This points towards the constellation of "Pisces" but it does slowly move and 2000 years ago it pointed towards "Aries" and so is called "the first point of Aries", or (since the sun is at the position in spring) the vernal equinox, $\gamma$.
No discussion of orbital elements is complete without the Wikipedia image which describes them.
The following is multiple choice question (with options) to answer.
Which direction does the sun, moon, and stars appear to travel? | [
"south to north",
"east to west",
"north to south",
"west to east"
] | B | Sun, Moon, and stars appear to travel from east to west each day. |
SciQ | SciQ-2049 | organic-chemistry, acid-base, hydrocarbons, halogenation
Sulfuric acid treatment serves to remove resinous materials, oil,
unsaturated hydrocarbons, and other unstable substances from crude
wax, as well as to remove polycyclic aromatic compounds, by treatment
with 102-103% oleum and subsequent neutralization with caustic.
After sulfuric acid treatment, the wax may contain free sulfuric acid
or caustic, the presence of which is explained either by incomplete
neutralization of the acid after treatment or by incomplete washing of
the caustic used in neutralizing the acid. The presence of either
acids or alkalis in waxes is extremely undesirable, since such
materials will cause corrosion of metals under the conditions of
production, use, and storage. These impurities in commercial paraffin
waxes are the cause of undesirable processes of oxidation, resin
formation, and decomposition. Apart from free sulfuric acid,
derivatives such as sulfonic acids and acid esters may be present in
paraffin. These are equivalent to the mineral acid in chemical action.
A negative result from the test of a petroleum product for free acid
or alkali still does not guarantee that these compounds will not be
formed in the petroleum product. If the product contains salts of
sulfonic acids, acid esters, naphthenic acids, or byproduct compounds,
then the action of high temperature or moisture (hydrolysis) will
quite probably result in the formation of acidic substances of a
mineral nature.(3)
References
The following is multiple choice question (with options) to answer.
Sulfate is used as a cleaning agent because it is acidic and soluble in what substance? | [
"air",
"salt",
"oxygen",
"water"
] | D | sulfate is used as a cleaning agent because it is water soluble and acidic. |
SciQ | SciQ-2050 | human-anatomy, muscles
Title: Contracting muscles in humans I study biology at school, and unfortunately for me, my program skips the muscles in humans chapter.
I know (and mainly, feel) that the movement in one direction isn't created by the same muscle as the movement in the opposite direction, e.g the Triceps ("front") and Biceps ("back").
I know that the triceps straightens the elbow, while the biceps contracts the elbow.
I also know that, instead of actually moving the arm, I can contract these two muscles (when I show off, for example...) without actually moving the arm. That area becomes hard. Both muscles, as I feel, are contracting. I cannot statically contract only one of them.
My question is whether this action is something "special", or simply both muscles working against each other, resulting in zero movement? The situation you are describing where muscles are situated on opposites sides of a joint and produce opposing movements is called "antagonism." Most joints are set up where one or more muscles on either sides will produce such movements (e.g., flexors vs. extensors). Here's a question about muscles without antagonists.
When you contract all the muscles crossing a joint (i.e., when you are "showing off"), the muscles balance each other. If not, the bones would move and the joint angles would change. So taking the elbow as an example, in the image below, Arnold is contracting the elbow flexors (biceps brachii, brachialis) as well as the elbow extensors (triceps brachii). In order for the bones to remain static, the forces must be equal and opposite.
The following is multiple choice question (with options) to answer.
Triceps and biceps muscles in the upper arm are an example of what type of muscle relationship? | [
"symbiotic",
"opposing",
"competitive",
"synchronized"
] | B | Triceps and biceps muscles in the upper arm are opposing muscles. |
SciQ | SciQ-2051 | terminology, metabolism, energy-metabolism
As Wikipedia puts it (emphasis mine):
An endotherm is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat released by its internal bodily functions instead of relying almost purely on ambient heat.
That really does seem to better match the "exo-" prefix.
Is there a real inconsistency here, or do I just understand this incorrectly? The prefix "endo" comes from the Greek "endon" meaning "inner". "Therm" comes likewise from the Greek "therme" meaning heat.
Thus Endo = inner, Therm = heat, heat from inside!
The confusion applies in chemistry, not in that someone has it wrong, but that molecular reactions sometimes release heat - this is obviously to the outside so it must be "exo". The Greek opposite of exo is endo, so the converse reaction (absorbing heat) must be endothermic.
Note also that in the case of an endothermic reaction, the heat supplied for the reaction to work comes from within the materials of the reaction, it's just that in the process of the reaction occurring the heat is "used up" so the reaction vessel feels cold. Because the heat is coming from inside the reaction "endo" makes sense here too.
I did my basic chemistry too long ago for me to remember for endothermic reactions if environmental heat is needed for the reaction to proceed, but I suspect that at any temp above 0 K, the answer is generally no; the heat comes from breaking of intra-molecular bonds.
The following is multiple choice question (with options) to answer.
Internal metabolism and the external environment are the sources of heat for what? | [
"hemeostasis",
"bioaccumulation",
"optimization",
"thermoregulation"
] | D | |
SciQ | SciQ-2052 | energy, electrostatics, potential-energy
Title: where is electrostatic potential energy stored?
Potential energy can be defined as the capacity for doing work which arises from position or configuration.In the electrical case, a charge will exert a force on any other charge and potential energy arises from any collection of charges.
Where is this potential energy stored and how? That actually gets a bit tricky at the advanced level, but at the basic level, you should find somewhere in your textbook the equation $U = \int d^3x \left(\frac{1}{2} |\vec{E}|^2 \right)$ (maybe with a different constant up front, depending on what system of units the book is using). So at any point in space, the electric field $\vec{E}(\vec{x})$ at that point "stores" an amount of potential energy $\frac{1}{2} |\vec{E}|^2$.
The following is multiple choice question (with options) to answer.
What is another term for stored energy? | [
"potential energy",
"latency",
"mechanical energy",
"inertia"
] | A | Did you ever see a scene like the one in Figure below ? In many parts of the world, trees lose their leaves in autumn. The leaves turn color and then fall from the trees to the ground. As the leaves are falling, they have kinetic energy. While they are still attached to the trees they also have energy, but it’s not because of motion. Instead, they have stored energy, called potential energy . An object has potential energy because of its position or shape. For example leaves on trees have potential energy because they could fall due to the pull of gravity. |
SciQ | SciQ-2053 | organic-chemistry, reaction-mechanism, nucleophilic-substitution
Title: How to determine whether inversion takes place?
Predict in which of the following reaction inversion of configuration takes place:
In my view, C) involves $\mathrm{S_{N} i}$ and therefore doesn't involve inversion of configuration. In D) the syn addition of $\ce{H2}$ across the double bond takes place and doesn't change the configuration. However I am not sure about A) and B). Any ideas?
A) is $\mathrm{S_N2}$ due to the secondary $\ce{C}$ and the sufficiently good nucleophile $\ce{I-}$. So inversion takes place.
B) is $\mathrm{S_N1}$ due to the tertiary $\ce{C}$. The solvent is also more polar than in A). So the stereochemical information would be lost.
The following is multiple choice question (with options) to answer.
What occur when elements switch places in compounds? | [
"chemical interaction",
"chain reaction",
"replacement reactions",
"chemical reaction"
] | C | Replacement reactions occur when elements switch places in compounds. In a single replacement reaction, one element takes the place of another in a single compound. In a double replacement reaction, two compounds exchange elements. |
SciQ | SciQ-2054 | human-biology, cardiology
Title: How can a heart of human work if one of its valve is not working? Yesterday I went to a hospital and heard a doctor say that one of the heart valves of a patient is not working. However, the patient was still alive and was healthy; the patient could walk and talk too. I could not understand it because I have read that all valves of heart are extremely important. I have tried searching on google but all I could find was heart attack problems. It is not possible that one of the valve is completely closed and the person is still alive without being in ICU. I think what the doctor was trying to communicate to the patient was that one of the valves is in the process of complete closure. There are three main types of diseases associated with heart valves :-
1- Blood flows backwards
2- Heart valve opening becomes narrow
3- upper condition may lead to complete closure
For details see the following link:-
http://www.nhlbi.nih.gov/health/health-topics/topics/hvd
http://en.wikipedia.org/wiki/Pulmonary_atresia
Hope you understand. :)
The following is multiple choice question (with options) to answer.
What does the human heart do? | [
"use blood",
"pump blood",
"make blood",
"destroy blood"
] | B | The heart of a resting adult pumps blood at a rate of 5.00 3 L/min. (a) Convert this to cm /s . (b) What is this rate in m 3 /s ? 3. Blood is pumped from the heart at a rate of 5.0 L/min into the aorta (of radius 1.0 cm). Determine the speed of blood through the aorta. Blood is flowing through an artery of radius 2 mm at a rate of 40 cm/s. Determine the flow rate and the volume that passes through the artery in a period of 30 s. The Huka Falls on the Waikato River is one of New Zealand’s most visited natural tourist attractions (see Figure 12.29). On average the river has a flow rate of about 300,000 L/s. At the gorge, the river narrows to 20 m wide and averages 20 m deep. (a) What is the average speed of the river in the gorge? (b) What is the average speed of the water in the river downstream of the falls when it widens to 60 m and its depth increases to an average of 40 m?. |
SciQ | SciQ-2055 | bond, atoms, molecules, valence-bond-theory
So the short answer to your first question is: "Molecular orbitals hold atoms together in covalent bonds, and those are a result of electrostatic interactions and the quantum nature of electrons."
Yes, ionic compounds are large collections of ions, and you can't really define "molecules" for them - instead we talk about "formula units" which are the lowest possible whole-number ratio of elements that represent the compound. Groups of covalently bonded atoms are also held together by electrostatic interactions, but since the covalent bonds are so much stronger, a molecular compound can exist "on its own" as a single molecule. Collectively, the forces that hold collections of molecules together are called van der Waals forces if they don't involve ions. In any atom or molecule, there is never a completely uniform charge density on the surface. For some molecules, this is extreme (water is a good example) and we say it is very polar, or that it has a large dipole moment. This is just another way of saying that one part has a negative charge and the other has a positive charge. In water it looks like this (from wikipedia):
In this picture, red means "more electrons" and blue means "less electrons." Water can form hydrogen bonds, which are very strong electrostatic interactions. Some atoms and molecules have an almost uniform charge density on the surface. We call these "non-polar" molecules - noble gases are good examples. However, even noble gases have what is called an induced dipole due to statistically correlated fluctuations in electron density when the atoms are near each other. As a result, even noble gases can be cooled to the point where they become liquid - the very, very weak electrostatic interactions will hold them together at low temperature, when they are not moving very fast. These forces are called London Dispersion Forces - after the guy who first described them. London dispersion forces are important, because they are found in all molecules - polar or not. In fact, this is what makes most plastics solid. Polyethylene, for example, is made of very long chains of essentially non-polar molecules (from wikipedia):
The following is multiple choice question (with options) to answer.
What bond is the force of attraction that holds together positive and negative ions? | [
"Electric",
"magnetic",
"ionic",
"Protonic"
] | C | An ionic bond is the force of attraction that holds together positive and negative ions. It forms when atoms of a metallic element give up electrons to atoms of a nonmetallic element. Figure below shows how this happens. |
SciQ | SciQ-2056 | If the papillae (bumps on your tongue) can sense 5 basic tastes
and any combination of those tastes produce a unique taste,
how many possible unique tastes can you have?
. . $\displaystyle \begin{array}{ccccc} \text{1-at-a-time:} & _5C_1 &=& 5 \\ \text{2-at-a-time:} & _5C_2 &=& 10 \\ \text{3-at-a-time:} & _5C_3 &=& 10 \\ \text{4-at-a-time:} & _5C_4 &=& 5 \\ \text{5-at-a-time:} & _5C_5 &=& 1 \\ \hline & \text{Total:} && {\color{blue}31} \end{array}$
Call the five basic tastes: $\displaystyle a,b,c,d,e$
You can list them and count them yourself . . .
. . $\displaystyle \begin{array}{ccc}\text{1-at-a-time:} & a,b,c,d,e \\ \\ \text{2-at-a-time:} & ab,ac,ad,ae,bc\\ & bd,be,cd, ce, de \\ \\ \text{3-at-a-time:} & abc, abd, abe, acd, ace \\ & ade, bcd, bce, bde, cde \\ \\ \text{4-at-a-time:} & abcd, abce, abde, acde, bcde \\ \\ \text{5-at-a-time:} & abcde \end{array}$
6. Originally Posted by Soroban
Hello, Masterthief1324!
I agree with skeeter and Dinkydoe . . .
The following is multiple choice question (with options) to answer.
There are five primary tastes in humans: sweet, sour, bitter, salty, and what? | [
"umami",
"tangy",
"aroma",
"hot"
] | A | 36.3 Taste and Smell There are five primary tastes in humans: sweet, sour, bitter, salty, and umami. Each taste has its own receptor type that responds only to that taste. Tastants enter the body and are dissolved in saliva. Taste cells are located within taste buds, which are found on three of the four types of papillae in the mouth. Regarding olfaction, there are many thousands of odorants, but humans detect only about 10,000. Like taste receptors, olfactory receptors are each responsive to only one odorant. Odorants dissolve in nasal mucosa, where they excite their corresponding olfactory sensory cells. When these cells detect an odorant, they send their signals to the main olfactory bulb and then to other locations in the brain, including the olfactory cortex. |
SciQ | SciQ-2057 | cellular-respiration
Title: Do cold blooded animals generate any heat? In explaining energy and work to an 8 year-old I said that all conversion of energy generates heat as a by-product. For example, cars generate heat in their engines and running generates heat in our bodies. Then the 8 year-old said, except for cold-blooded animals.
So my question is, do cold-blooded animals generate any heat in their conversion of stored energy (food, fat, etc) into motion? If they generate heat, why are they cold-blooded? They do generate heat. They just do not SPEND energy specifically on heating their bodies by raising their metabolisms. This is a form of energy conservation. The metabolic rate they need to live is not nearly enough to heat their bodies.
An example of spending energy to heat the body is seen in humans shivering. Here muscle is activated not for its usual purpose, but to function as a furnace. "Warm-blooded" and "cold-blooded" is somewhat a misnomer. The correct way to think of it is...
Endotherm or ectotherm. Does the heat primarily come from within (endo) or from the surroundings (ecto). Endothermic animals include mammals. Most of their body heat is generated by their own metabolisms. Ectothermic animals include reptiles and insects. They absorb most of their body heat from the surroundings. This is not the same as saying they let their body temperature fluctuate with their surroundings, some avoid this by moving around to accomodate themselves.
Homeotherm or poikilotherm. Homeotherms want to maintain homeostasis for their body temperatures. They don't want it to change. Poikilotherms do not exhibit this behaviour, instead their body temperatures vary greatly with the environment.
We can have endotherm poikilotherms, such as squirrels, who let their body temperature drop while hibernating. Endotherm homeotherms, such as humans, where temperature is constant by means of complex thermoregulation. Ectotherm homeotherms, such as snakes (moving into shadow or into the sun to regulate temperature), and ectotherm poikilotherms, such as maggots.
The following is multiple choice question (with options) to answer.
Are birds and mammals mainly exothermic or endothermic? | [
"exothermic",
"autotrophic",
"hypothermic",
"endothermic"
] | D | |
SciQ | SciQ-2058 | waves, oscillators, string
Is the principal the same as for the transverse waves? There is a few reasons why I can't really see that working: the rotational waves in this case are sometimes so large that the flat part goes vertical (i.e. against the wind) or even rotates by multiple revolutions.
The most important one: Why is the wavelength of the rotation waves (i.e. the separation of the nodes as can be seen in the picture) so much lower than for the transverse waves? This is an observation that is not obvious from the picture, but usually there are only like 3 or 4 oscillations nodes for the transverse ones and like 30 for the rotational ones.
The question will get too broad if I ask more questions about this, so let's focus on the above. I am generally interested in this phenomenon and there are other questions I can't quite answer (e.g. when it is not very windy there aren't any oscillations and sometimes when the wind is weak oscillations come and go. So why is there a "critical wind speed" at which they start resonating up?). I'm having a problem visualizing the transverse waves with 3 or 4 nodes you mention. All videos I've found show standing waves with only two nodes, the slackline moving up and down between the anchor points (or between an anchor point and the person walking the slackline).
The rotation waves I saw (maybe torsion oscillation is a better name) also had only two nodes. The "nodes" in the picture aren't actual nodes, they are points where the twist angle corresponds to the viewing angle. If the middle of the line makes (a bit more than) seven complete rotations, you'll have 14 positions on the left and on the right where the rotation is a multiple of 180 degrees, giving you 28 visual points. Their number indicates the amplitude of the torsional oscillation rather than the number of nodes.
The following is multiple choice question (with options) to answer.
What are the high points in a transverse wave called? | [
"waves",
"peaks",
"crests",
"apex"
] | C | A transverse wave is characterized by the high and low points reached by particles of the medium as the wave passes through. The high points are called crests, and the low points are called troughs. You can see both in the Figure below . |
SciQ | SciQ-2059 | electrical-engineering, chemistry
Title: What is the field on engineering that combines chemistry and electronics together? I am looking for a career advice as I am interested in chemistry and electronics at the same time but the universities somehow have the two as different major. Is there any branch of engineering that combines the two? You could follow either Chemistry (Science), Chemical Engineering or Electrical Engineering and purse a career in Semiconductors. There are many variation in Semiconductor that fall either into chemistry or electronics. Below is small sample of options
Semiconductor Lithography Systems
MEMS Technology
Semiconductor Failure Analysis
Silicon Wafer Processing
Microfluidics and microfluidic devices
The following is multiple choice question (with options) to answer.
Chemistry and physics are fields in what type of science? | [
"Biology",
"physical",
"Botany",
"Meteorology"
] | B | The space shuttle program has been very successful. Over 100 mission have been flown. Space shuttle missions have made many scientific discoveries. Crews have launched many satellites. There have been other great achievements in space. However, the program has also had two tragic disasters. |
SciQ | SciQ-2060 | ecology
I have tried to find explanatory texts both in this and other books without any success so my question is how's this balanced state achieved in both types of successions (the answer is hinted in the first paragraph which I don't quite understand)?
Related to my last post. The author is saying that 1) Mature ecosystems tend to have a balance between production (=P) and use (=R, respiration) of biomass. This is actually tautological because the author would probably define a mature ecosystem as one where this is true (P=R).
If it starts out P > R, the autotrophs are dominant: more biomass is being produced than used up. It is possible, for a time, that P will increase as, for example, plants grow more leaves, but R is growing too, and there is an eventual limit on P, which at maximum depends on the light available to the ecosystem. As biomass grows, so does the amount of biomass to potentially decay, so eventually R will always catch up to P, until there is balance.
If it starts out P < R, that means you are using up biomass faster than you are creating it. This case is even simpler: you will gradually run out of biomass, and R will decrease.
In either case, when the author is talking about P = R, this is going to be in relative terms; there might still be variations between them, for example seasonal variation, but on average over years or decades you would expect P = R in a mature, stable ecosystem.
The following is multiple choice question (with options) to answer.
Pyramids of net production and biomass reflect what level of efficiency? | [
"high",
"extreme",
"low",
"medium"
] | C | |
SciQ | SciQ-2061 | electric-circuits, electric-current, electrical-resistance, voltage
The “rate of flow” of charge is simply charge/time and this calculation for a circuit gives you the number of coulombs that went past a point in a second. This is just what current is.
Resistance is a circuit’s resistance to current; it is, like you said, measured in ohms, but it is caused by the vibrations of atoms in a circuit's wire and components, which results in collisions with electrons, making charge passage difficult. This increases with an increase in temperature of the circuit, as the atoms of the circuit have more kinetic energy to vibrate with.
Voltage is the energy in joules per coulomb of electrons. This is shown though the equation E=QV where the ratio of Energy over charge= voltage. This is granted by the battery, which pushes coulombs of electrons, with what we call electromotive force. However when it is said that the potential difference across a component is X volts, it means that each coulomb is giving X joules of energy to that component.
Note: if an equation doesn’t make intuitive sense to you, chances are it is a complicated derivation, and to understand it you’ll have to learn its derivation.
The following is multiple choice question (with options) to answer.
The rate of flow of charge in an electrical circuit is known as what? | [
"velocity",
"voltage",
"output",
"current"
] | D | Figure 20.2 The rate of flow of charge is current. An ampere is the flow of one coulomb through an area in one second. |
SciQ | SciQ-2062 | ichthyology, vertebrates
Title: If an organism is supported only by cartilage, does it have an endoskeleton? Lamprey and sharks lack bones, but does this mean they are not classified as having an endoskelton? Does an organism need bone to be considered as having an endoskeleton? From wikipedia
An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.
Cartilage is a mineralized tissue so it counts as a skeleton from this definition. A bit further in the wikipedia article it says
The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage)
The following is multiple choice question (with options) to answer.
The vertebrate endoskeleton can also be called what? | [
"structural skeleton",
"internal skeleton",
"deep skeleton",
"exoskeleton"
] | B | The vertebral column is the core of the vertebrate endoskeleton, or internal skeleton. You can see a human skeleton as an example of the vertebrate endoskeleton in Figure below . In addition to the vertebral column, the vertebrate endoskeleton includes:. |
SciQ | SciQ-2063 | cell-biology, cancer, pharmacology, cell-culture, assay-development
Title: How much effort is it to establish a cytotox assay for cancer cell lines against a small number of possible compounds? I am currently testing a series (5-10) of small molecule compounds against an enzyme that are intended as inhibitors. This enzyme is meaningful for cell proliferation.
Until now, nothing was active and therefore I could try to test the new molecules in a cytotox assay, to test if they are of any medicinal value. It is known, that these compounds have multiple modes of action and inactivity against the discussed enzyme does not necessarily mean that they are fully inactive.
I am wondering how complicated this is and if you're a beginner on this how long does it take to set up a growth inhibition or viability assay. Currently me gathered experience on protein expression and aspetic technique. But I have no experience with cell culture and sterile bench. My cell lines of interest are melanoma cell lines and or various brest cancer cell lines that are commercially available from multiple known suppliers. Do you think it would be possible to test this in a couple of weeks? I am willing to work 7 days per week if this will speed up the process. What is a realistic time frame to get first results? I would work with commercial inhibitors as control. I have no idea how time intense this process might be and would be interested about your insights. The answer to this is, of course, "it depends". There are quite a few factors at play here. As you don't seem to be experienced at cell culture yet, I strongly recommend that you find someone experienced to teach you. It is not something that is easy to pick up, as problems in cell culture (e.g. low-level contamination, cross-contamination, old cells, overgrowth, under-seeding) can be subtle and difficult to identify without experience.
It will take at least 4 weeks for experience to kick in, and cells aren't like bacteria in that they won't grow overnight to suitable levels for sub-culturing/experimentation; it'll take days to weeks of growth from a frozen vial to having enough to work with. This takes time alone. You'll need to be in some weekends anyway; when cells need to be split or fed, that's when you'll be in!
The following is multiple choice question (with options) to answer.
What can be used to speed up biochemical reactions? | [
"carbohydrates",
"proteins",
"enzymes",
"hormones"
] | C | pH values for several common materials are listed. |
SciQ | SciQ-2064 | atmospheric-chemistry
But some researchers have argued it does make a notable contribution in the lower atmosphere, but indirectly. There doesn't appear to be a consensus on how big this effect is (and the Wikipedia reference is old and obsolete). The argument for ozone being a notable contributor is based on the following. Hydrocarbon pollution in the lower atmosphere (often from vehicle emissions) leads to a variety of undesirable reactions some of which lead to the production of ozone (as well as many other irritating components of smog). We really don't want too much smog or ozone in the lower atmosphere because it is bad for health. Some have estimated that it also adds to the warming caused by hydrocarbon emissions (exacerbating the warming potential of methane, for example).
It is hard to judge the estimates of its contribution to warming not least because they rely on models of complex reactions caused indirectly by other pollutants. Also, the big issue with emissions leading to ozone are not its contribution to warming but its contribution to pollution which causes direct harm to people in the short term. In fact regulations around emissions has been striving to reduce those emissions since before we started worrying about global warming. And, many countries have sharply reduced them (this is a major reasons why most western countries insist on catalytic converters in their vehicles). We should reduce ozone pollution by reducing the other emissions that cause it and we have been doing that for decades.
I would argue that ozone is essentially irrelevant to global warming. We should strive to reduce it in the lower atmosphere even if we were not worried by global warming. So even if we can't agree on how big its contribution to warming is (which the literature isn't clear on) we should be reducing it as much as we can for more direct reasons.
And, even if we wanted to report its contribution to warming, the best place to account for it is to add it to the contribution of other emissions (eg methane) rather than to account for it separately as we don't directly emit it from anything.
The following is multiple choice question (with options) to answer.
The abundance of this substance in the atmosphere is what most scientist agree that is causing global warming? | [
"iron oxide",
"liquid dioxide",
"carbon dioxide",
"argon"
] | C | Most scientists agree that global warming is caused by more carbon dioxide in the atmosphere (see Figure below ). This increases the greenhouse effect. There is more carbon dioxide mainly because of the burning of fossil fuels. Destroying forests is another cause. With fewer forests, less carbon dioxide is removed from the atmosphere by photosynthesis. |
SciQ | SciQ-2065 | human-biology, surgery
Title: Is there a simple incision that would render a man impotent? I’m writing a novel in which two women (one of whom is a doctor) take revenge on a rapist by performing surgery on him.
What would be the simplest but most effective way of causing permanent and total erectile dysfunction?
I assume cutting one or more nerves but there are several up for contention:
The Dorsal nerve
Pudendal nerve
Inferior rectal nerve
Perineal nerve
Posterior scrotal nerves
Ideally, I’d like the surgery to be so minimally invasive that he wouldn’t even be aware that it had been done to him. You want to somehow damage the cavernous nerves of the penis. If you damage the preganglionic root of the cavernous nerves (the pelvic splanchnic nerve), you'll create all kinds of other problems.
You might also consider using a chemical agent instead of surgery; this will allow for increased discretion and ease of administration. I discuss this after the break in my answer.
Erection is driven by the parasympathetic nervous system; ejaculation is driven by the sympathetic nervous system. Since you're looking for "permanent and total erectile dysfunction," you want to disrupt parasympathetic innervation to the penis. The candidates you've mentioned (dorsal nerve, pudendal nerve, inferior rectal nerve, perineal nerve, posterior scrotal nerves) won't work since none of them provide parasympathetic innervation to the penis. Rather, the dorsal nerve of the penis is a branch of the pudendal nerve and provides sympathetic (ejaculation) and sensory innervation; the inferior rectal nerves are also branches of the pudendal nerve and provide purely somatic innervation to the anus (these lie below the pectinate line, which marks the boundary we use to define internal and external hemorrhoids); the posterior scrotal nerves are a sensory branch of the perineal nerve, which itself is a branch of the pudendal nerve. This plate from Gray's will help you visualize these relationships.
The following is multiple choice question (with options) to answer.
Most cases of syphilis can be cured with what? | [
"enzymes",
"vitamins",
"antibiotics",
"abstinence"
] | C | Syphilis is less common than chlamydia or gonorrhea but more serious if untreated. Early symptoms of syphilis infection include a small sore on or near the genitals. The sore is painless and heals on its own, so it may go unnoticed. If treated early, most cases of syphilis can be cured with antibiotics. Untreated syphilis can cause serious damage to the heart, brain, and other organs. It may eventually lead to death. |
SciQ | SciQ-2066 | water, mountains
Title: How do mountain springs get their water? I am curious how do mountain springs get their water. The water flowing from them eventually forms rivers.
Is it only from rain and snow? Or does water also come from underground-below the mountain (if so, then how does it "climb" to the spring which is at a high altitude)? Ultimately, it comes from precipitation. Ordinarily we think of rain as coming from low-level clouds, but Putkonen[1] has compiled rainfall data in the Himalayas showing significant rains up to several thousand meters altitude, covering the range where practically everyone lives. It is this precipitation that fills the underground tables mentioned by Jean-Marie Prival in a comment to the question.
Such a source is subject to the effects of climate change, which accordingly has led to significant environmental issues. See Ref [2].
References:
1.
Jaakko K. Putkonen, "Continuous Snow and Rain Data at 500 to 4400 m Altitude near Annapurna, Nepal, 1999–2001", Arctic, Antarctic, and Alpine Research, 36:2, 244-248 (2004)
2.
Sandeep Tambe, Ghanashyam Kharel, ML Arrawatia, Himanshu Kulkarni, Kaustubh Mahamuni, Anil K Ganeriwala,
"Reviving dying springs: climate change adaptation experiments from the Sikkim Himalaya",
Mountain Research and Development 32 (1), 62-72 (2012)
The following is multiple choice question (with options) to answer.
How can people access water in an aquifer that does not flow from a spring or a geyser? | [
"mound building",
"generate electricity",
"evaporation",
"dig a well"
] | D | Most groundwater does not flow out of an aquifer as a spring or geyser. So to use the water that's stored in an aquifer people must go after it. How? They dig a well. A well is a hole that is dug or drilled through the ground down to an aquifer. This is illustrated in Figure below . |
SciQ | SciQ-2067 | ichthyology, vertebrates
Title: If an organism is supported only by cartilage, does it have an endoskeleton? Lamprey and sharks lack bones, but does this mean they are not classified as having an endoskelton? Does an organism need bone to be considered as having an endoskeleton? From wikipedia
An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.
Cartilage is a mineralized tissue so it counts as a skeleton from this definition. A bit further in the wikipedia article it says
The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage)
The following is multiple choice question (with options) to answer.
What is the term for animals that have a backbone? | [
"herbivores",
"vertebrates",
"carnivores",
"invertebrates"
] | B | The first eight phyla listed in Table above include only invertebrate animals. Invertebrates are animals that lack a vertebral column , or backbone . The last phylum in the table, the Chordata, also includes many invertebrate species. Tunicates and lancelets are both invertebrates. Altogether, invertebrates make up at least 95 percent of all animal species. The remaining animals are vertebrates. Vertebrates are animals that have a backbone. All vertebrates belong to the phylum Chordata . They include fish, amphibians, reptiles, birds, and mammals. |
SciQ | SciQ-2068 | zoology, entomology, species-identification
Title: What flying insect is this?
Found in Russia. Approx. 7 cm. This is Crane fly, of the Tipulidae family. They don't bite humans, adults feed on nectar. Larvae prefer moist environments such as wet soil or decomposing vegetable matter and can consume roots and vegetation, damaging plants. Among others, bats and some Coleoptera are its predators.
Further informations can be found in the Wikipedia article linked above.
The following is multiple choice question (with options) to answer.
What type of animal that eats only or mainly insects? | [
"heterotrophic",
"invertebrates",
"anaerobic",
"herbivores"
] | A | heterotrophic animal that eats only or mainly insects. |
SciQ | SciQ-2069 | biochemistry, ecology, marine-biology, climate-change
So... raising temps can cause less mixing of water due to more stratification (layering), which results in less water in the ocean available to absorb and hold the CO2. This means that as atmospheric CO2 continues to increase, the non-mixing surface layer of ocean water (which will become saturated with CO2 at some point) won't be able to keep up with more and more and more CO2 in the air. As a result, the ocean will decline (and eventually potentially fail) in its ability to "buffer" the ever increasing CO2 in the air. This would mean that the rate of CO2 in the air will start increasing more rapidly (since less and less of it is being absorbed by the oceans).
As for the phytoplankton (which are in this top layer of water), this stratification will not directly result in less CO2 availability to them. As atmospheric CO2 increases, so will the amount in this top layer of water. The rate of increase in CO2 concentration will just slow until a saturation point is reached, but absolute levels will not decline.
Though, note, however, that phytoplankton tend to thrive in areas of high nutrients (i.e., upwelling zones). Less mixing of waters will decrease the upwelling of nutrient-rich, cooler subsurface water. So less mixing (i.e., more stratification) likely would lead to declines in phytoplankton abundance due to decreased nutrients availability. (See here). Perhaps this decreased nutrient availability (which would include loss of carbon sources) is related to what you're referring to?
Read here for some more thoughts: https://earthobservatory.nasa.gov/features/OceanCarbon
Raising Temperatures may decrease CO2 solubility
However, given all this, the solubility of CO2 in water does decline with increasing temperature (see here for raw data). This suggests that some rise in global temps may impact CO2 concentration in ocean waters.
The following is multiple choice question (with options) to answer.
What do you call the zone in a body of water where there is too little sunlight for photosynthesis? | [
"Dark Zone",
"semimetal zone",
"observable zone",
"aphotic zone"
] | D | Neurons are usually classified based on the role they play in the body. Two main types of neurons are sensory neurons and motor neurons. |
SciQ | SciQ-2070 | sociality, olfaction
Sexual Signaling:
In some species, apocrine gland secretions may play a role in sexual attraction and mate selection. The distinct scents emitted by individuals can serve as cues for potential mates to assess each other's fitness and genetic compatibility.
Developmental Timing:
Apocrine glands are not fully functional until puberty in humans. Their activation and development are influenced by hormonal changes during adolescence.
Associated with Hair Follicles:
Apocrine glands are associated with hair follicles, and their ducts open into the hair follicle canal. This is in contrast to eccrine glands, which release sweat directly onto the skin's surface.
Here's a ref from nature stating that human primates may use sweat pheromones to communicate:
https://www.nature.com/articles/npre.2008.2561.1.pdf
Primates, especially those living in social groups, rely heavily on communication to maintain social bonds, establish hierarchies, and coordinate group activities. Scent plays a crucial role in primate communication, and sweat scent could have evolved as a means for individuals to convey information about their identity, reproductive status, and emotional state to other members of their group.
mate selection in primates can be influenced by olfactory cues. Scent signals emitted through sweat may allow potential mates to assess each other's genetic compatibility, overall health, and reproductive fitness.
the scent-marking behavior using secretions from sweat glands may serve as a way to establish territorial boundaries and prevent conflicts with neighboring groups.
The odor produced by sweat may play a role in avoiding predators. For example, certain primate species may produce alarm pheromones through their sweat, signaling danger to other group members.
Sweat scent in primates could be a remnant of their ancestral heritage, where scent communication was crucial for survival and reproduction.
incidentally, horses, dogs, deer, they also have strong pheromones.
The following is multiple choice question (with options) to answer.
The sweat glands of the armpit are classified as these? | [
"pineal glands",
"mucus glands",
"apocrine glands",
"adrenal glands"
] | C | Apocrine secretion accumulates near the apical portion of the cell. That portion of the cell and its secretory contents pinch off from the cell and are released. The sweat glands of the armpit are classified as apocrine glands. Both merocrine and apocrine glands continue to produce and secrete their contents with little damage caused to the cell because the nucleus and golgi regions remain intact after secretion. In contrast, the process of holocrine secretion involves the rupture and destruction of the entire gland cell. The cell accumulates its secretory products and releases them only when it bursts. New gland cells differentiate from cells in the surrounding tissue to replace those lost by secretion. The sebaceous glands that produce the oils on the skin and hair are holocrine glands/cells (Figure 4.11). |
SciQ | SciQ-2071 | biochemistry, proteins, enzymes
Title: Is chitin actually protein? Recently insects are featured as a protein rich source for human nutrition. That humans can really digest chitin through chitinase enzym has been only recently confirmed.
But, does the chitin shell of their body actually count to the protein family?
Wikipedia does not state a clear yes or no. It says it is derivative of glucose, and may be compared by function to keratin protein. I'd really like to exclude any ambuguity and undersrand why. Chitin and protein are completely unrelated.
The only common thing is that they are polymers.
Chitin is a polymer of amino sugars while protein is a polymer of amino acids.
Both monomers are very different and are not converted one to the other.
In fact, chitin, like cellulose, is not fragmented by animals, so it is not absorbed.
Moreover, chitin is a homopolymer, so even if it where absorbed and transformed to amino acids, it would yield only one (or maybe a few ones) but all the others would have to be obtained through a different source.
So chitin is not a source of protein or amino acids.
The following is multiple choice question (with options) to answer.
Chitin is a substance that is found in what part of animals like beetles and lobsters? | [
"tails",
"eggs",
"shell",
"brains"
] | C | The cell walls in many species of fungi contain chitin. Chitin is tough carbohydrate found in the shells of animals such as beetles and lobsters. The cell wall of a plant is made of cellulose, not chitin. |
SciQ | SciQ-2072 | atmosphere, temperature, humidity, atmospheric-optics
Source As described here, condensation of cloud particles (i.e., contrail formation) will occur if the mixing between hot and moist exhaust from an aircraft engine and ambient environmental air results in the mixed air exceeding the ice saturation vapor pressure as its temperature changes. A conceptual diagram of this mixing process is shown here, for exhaust (parcel A) and environmental air (parcel B) with generic temperatures and saturation vapor pressures is shown here:
However, this would require knowledge of these specific temperatures and corresponding saturation vapor pressures. More practically, contrail prediction often just assumes that the air at altitudes where jets typically cruise (commonly, though not always, above 8 km/26,000 ft and at air temperatures below -40°C) is near or above supersaturation with respect to ice. This assumption is used operationally, for example, in NASA's publicly-available persistent contrail forecast. Note that the first source indicates that low wind speeds are also useful in identifying likely regions of persistent contrails.
Several sources of data may be useful in constructing similar analyses or forecasts and comparing to what might be expected on an average day, based on the local climatology. Observational data from radiosondes (i.e., weather balloons with instruments measuring temperature, moisture, and winds) is available globally in near-real time. This provides actual measurements of weather conditions through the relevant altitudes for contrail formation, and is particularly useful if measurements are needed relatively close to a radiosonde launch site.
For broader coverage in both space and time, the US National Oceanic and Atmospheric Administration provides archives of past weather analyses and operational forecast model output that can be requested by the general public. These datasets contain gridded model output with common parameters at various levels through the atmosphere on a national to global scale. While these datasets do not strictly consist of observed measurements, they are useful for analyses extending beyond the relatively limited set of observations available in most circumstances. Output from various operational forecast models is available for near-current or future conditions, whereas the reanalysis datasets provide similar information obtained from model analyses of past weather.
The following is multiple choice question (with options) to answer.
What kind of air does a continental polar air mass hold? | [
"warm dry air",
"cool moist air",
"cold dry air",
"frigid wet air"
] | C | An air mass takes on the conditions of the area where it forms. For example, a continental polar air mass has cold dry air. A maritime polar air mass has cold moist air. Which air masses have warm moist air? Where do they form?. |
SciQ | SciQ-2073 | equilibrium, water, ions, terminology
Title: What kind of 'product' is the 'product' in 'ionic product of water'? My language has different words for product (=the result of a process) and product (=the sum of multiplied quantities), so I need to know the right meaning to choose the right word.
Which of the meanings above is present in the English term 'ionic product of water' ($K_\mathrm{w}$)?
This definition from http://www.chemguide.co.uk/physical/acidbaseeqia/kw.html seems to suggest it is a sum of multiplied quantities:
The units of $K_\mathrm{w}$: $K_\mathrm{w}$ is found by multiplying two concentration terms together. Each of these has the units of $\mathrm{mol~dm^{-3}}$. Multiplying $\mathrm{mol~dm^{-3}} \times \mathrm{mol~dm^{-3}}$ gives you the units above.
However, the use of the verb produce in this sentence from https://en.wikipedia.org/wiki/Self-ionization_of_water suggests something that is produced as a result of a process:
According to the theories of Svante Arrhenius, this must be due to the presence of ions. The ions are produced by the self-ionization reaction $\ce{H2O + H2O <=> H3O+ + OH-}$
Alternatively, could both meanings apply depending on your perspective?
Thanks in advance for any clarification. Per Zhe's comment, in the specific context of the term ionic product of water, the word product is used in the sense of the result of the mathematical operation of multiplication:
The ionic product of water equals the concentration of $\ce{H+}$ times the concentration of $\ce{OH-}$:
$$K_\mathrm w = \ce{[H+][OH-]}$$
The following is multiple choice question (with options) to answer.
What do you call taxes placed on products that produce carbon dioxide? | [
"emission tax",
"carbon taxes",
"chemical tax",
"pollution tax"
] | B | Carbon taxes are taxes placed on products that produce carbon dioxide. An example of this is gasoline for your car. The taxes encourage people to use less fossil fuel. This naturally reduces carbon dioxide emissions. |
SciQ | SciQ-2074 | Let us start with the target $$b_n$$, the last element of $${\bf b}$$. This must arise from some linear combination of the $$n$$th rows of columns $${\bf a_1}$$ to $${\bf a_n}$$, but since $${\bf A}$$ is upper-triangular, the columns $${\bf a_1} ... {\bf a_{n-1}}$$ all contain a zero in the $$n$$th row, that is the elements $$a_{n,1} ... a_{n,n-1}$$ are all zero. This means that only the $$n$$th column has any influence in determining the element $$b_n$$, in particular the product $$b_n = a_{n,n} x_n$$ determines the result. From this it follows that $$a_{n,n}$$ cannot be zero, for if it is zero, then $$b_n$$ must also be zero. And if $$b_n$$ is zero, then it is impossible to find an $${\bf x}$$ for {\em any} $${\bf b}$$ whenever $$b_n \not = 0$$. Thus $$a_{n,n}$$ is not zero.
Since $$a_{n,n}$$ is not zero, it analytically follows that $$x_n = b_n / a_{n,n}$$ for any target $$b_n$$. Thus the element $$b_n$$ in the vector $${\bf b}$$ has been correctly established. Furthermore, this is the {\em only} way the result can be obtained, since no other column holds any influence over the result, therefore the coefficient $$x_n$$ is also uniquely determined.
The following is multiple choice question (with options) to answer.
What does the coefficient in front of an element in a formula indicate? | [
"how much is involved in the reaction",
"place on the Periodic Table",
"time of the reaction",
"number of atoms"
] | A | In chemical equations, reactants and products are represented by chemical symbols and formulas. Numbers called coefficients are placed in front of the symbols and formulas to show how much of each substance is involved in the reaction. |
SciQ | SciQ-2075 | reinforcement-learning, rewards, intelligent-agent, learning-algorithms, environment
What happens if you continue training after the agent has learnt the environment? Will it perform by reaching its goal every time or will there be failed episodes?
If you include training episodes, then RL learns mainly by "trial and error". So you should expect an agent to make deliberate mistakes as it tests to see what happens. In some environments these could be critical mistakes leading to failed episodes.
If you ignore the training episodes and are interested only in performance without exploration - e.g. testing every few hundred episodes - then you can expect performance to vary depending on the type of agent and environment. Some agents even exhibit "catastrophic forgetting", which as the name implies causes performance to drop significantly - this can be caused by a successful agent over-fitting to all the recent successful episodes without errors it just experienced, and losing the ability to predict the true lower value of incorrect actions.
Neither failed episodes during training nor catastrophic forgetting are inevitable. It depends on the environment and type of agent.
The following is multiple choice question (with options) to answer.
Behaviors that occur naturally and are not learned are called what? | [
"adaptive",
"intuitive",
"innate",
"acquired"
] | C | Many animal behaviors are ways that animals act, naturally. They don’t have to learn how to behave in these ways. Cats are natural-born hunters. They don’t need to learn how to hunt. Spiders spin their complex webs without learning how to do it from other spiders. Birds and wasps know how to build nests without being taught. These behaviors are called innate. |
SciQ | SciQ-2076 | botany, plant-physiology, plant-anatomy
Title: Sporophyte and gametophyte
My textbook says that in both groups of seedless plants (vascular plants, non-vascular plants) the gametophyte is a free-living plant, independent of the sporophyte.
I don't understand this statement and am now wondering if the sporophyte and gametophyte are stages in a plant's lifecycle, or are they individual parts of the plant, or are the sporophyte and the gametophyte different plants altogether? Secondly, does this differ depending on the organism?
Different plants or different structures that make up the same organism? The sporophtye is the diploid stage in the life cycle. In comparison, with humans, you and I would be sporophytes.
The Gametophyte is the haploid stage in the life cycle. In comparison, with humans, spermatozoids and ovules are gametophytes.
The following is multiple choice question (with options) to answer.
Which is the dominant stage of the lifecycle of a fern? | [
"sporophyte",
"zygote",
"larvae",
"gametophyte"
] | A | The dominant stage of the lifecycle of a fern is the sporophyte, which consists of large compound leaves called fronds. Fronds fulfill a double role; they are photosynthetic organs that also carry reproductive organs. The stem may be buried underground as a rhizome, from which adventitious roots grow to absorb water and nutrients from the soil; or, they may grow above ground as a trunk in tree ferns (Figure 25.20). Adventitious organs are those that grow in unusual places, such as roots growing from the side of a stem. |
SciQ | SciQ-2077 | human-biology, senses
Olfaction (smell, as carried out by neurons in the nasal epithelium; e.g. smell of vanilla, and smell of bad food)
Gustation (taste, as carried out by neurons on the tongue; e.g. salt, sugar)
Antigen chemosensing (chemical sensing, as carried out by, for instance, immune antigen receptors on B cells)
Hormonal signaling chemosensing (chemical sensing of hormones such as insulin, as carried out for instance by myocytes)
Starch sensing? (amylase in saliva can be used as a test for digestable starch)
Visual system, at the retina?
Visible light (sensing electromagnetic radiation on the order of a few hundred nanometers in wavelength)
Internal methanol sensing (the visual system as a sensor for methanol, which disproportionately affects myelin surrounding the optic nerve)
Pressure sensing (see phosphenes)
The vestibular system
Gravity sensing
Balance
Coordination
Motion sensor
Head position sensor
Spatial orientation
Skin
thermosensation (touching a hot kettle!)
Nociception (pain sensing)
allergen sensing
sensor for gamma rays, X-rays and UV light (indicated by radiation burns, development of skin cancer, sunburns, etc.)
Bones and muscles?
Kinesthetic and bodily proprioception
Brain/mind/mental/social senses?
mental pain
boredom
mental or spiritual distress
sense of self and other, including friendship, power, place in social hierarchy, reputation, companionship
motivation and love (oxytocin, dopamine, etc. in limbic systems and other neural correlates)
I'm sure some would agree, and some would disagree about the specific cases I provide. Thus the definition of senses, or sensing, seems to be opinion-based or at the very least very sensitive to an agreed-upon operational definition, for which there is none.
The following is multiple choice question (with options) to answer.
What is a specific region in space within which a sensory receptor is responsive to stimuli? | [
"symmetrical field",
"receptive field",
"deceptive field",
"amplify field"
] | B | CHAPTER SUMMARY 36.1 Sensory Processes A sensory activation occurs when a physical or chemical stimulus is processed into a neural signal (sensory transduction) by a sensory receptor. Perception is an individual interpretation of a sensation and is a brain function. Humans have special senses: olfaction, gustation, equilibrium, and hearing, plus the general senses of somatosensation. Sensory receptors are either specialized cells associated with sensory neurons or the specialized ends of sensory neurons that are a part of the peripheral nervous system, and they are used to receive information about the environment (internal or external). Each sensory receptor is modified for the type of stimulus it detects. For example, neither gustatory receptors nor auditory receptors are sensitive to light. Each sensory receptor is responsive to stimuli within a specific region in space, which is known as that receptor’s receptive field. The most fundamental function of a sensory system is the translation of a sensory signal to an electrical signal in the nervous system. All sensory signals, except those from the olfactory system, enter the central nervous system and are routed to the thalamus. When the sensory signal exits the thalamus, it is conducted to the specific area of the cortex dedicated to processing that particular sense. |
SciQ | SciQ-2078 | geology, mineralogy, minerals, metamorphism
Title: Is there any mineral that survives hard degree metamorphism? When a protolith enters in metamorphism, the minerals transform in other new stable minerals while the pressure and/or temperature increase.
Is there any mineral that would not be affected by a high degree metamorphism processes and would remain the same without experiencing any change? Zircon is one mineral which survives metamorphism.
Zircons can survive processes like erosion, transport and metamorphism, so they preserve a record of past geological processes.
From Wikipedia,
Zircon is common in the crust of Earth. It occurs as a common accessory mineral in igneous rocks (as primary crystallization products), in metamorphic rocks and as detrital grains in sedimentary rocks.
This makes zircon very useful in determining the age of rocks.
The following is multiple choice question (with options) to answer.
What changes from heat or pressure during metamorphism? | [
"grains",
"fossils",
"minerals",
"carbohydrates"
] | C | Metamorphism does not cause a rock to melt completely. It only causes the minerals to change by heat or pressure. If the rock melts completely, it will cool to become an igneous rock. |
SciQ | SciQ-2079 | condensed-matter
Title: If a liquid is compressed enough, would it become solid? If a liquid were to be compressed so tensely that the particles had no room to move, would it then become a solid?
Also, would the same happen with a gas? It depends on the substance. It is easy to work out though from the relevant phase diagram.
Isothermally increasing the pressure of liquid CO$_2$ will create a solid phase (dry ice). But increasing the pressure of liquid water will not create ice.
A gas-to-solid transition with increasing pressure is a process called deposition. It will happen with most substances if the temperature is sufficiently low.
The following is multiple choice question (with options) to answer.
Do most substances increase or decrease in size when they change from a liquid to a solid? | [
"decrease",
"increase",
"it is unable to be measured",
"stay the same"
] | A | This is how ice wedging works. When liquid water changes into solid ice, it increases in volume. You see this when you fill an ice cube tray with water and put it in the freezer. The ice cubes go to a higher level in the tray than the water. You also may have seen this if you put a can of soda into the freezer so that it cools down quickly. If you leave the can in the freezer too long, the liquid expands so much that it bends or pops the can. (For the record, water is very unusual. Most substances get smaller when they change from a liquid to a solid. ). |
SciQ | SciQ-2080 | waves
I found it helpful seeing this image together with Davide Dal Bosco's answer. Allow me to drop the complex notation, as it is useful to do the computations, but at the end usually one takes only the real part to get the result.
A travelling wave can be expressed, as you correctly say as
\begin{equation}
\phi^+(x, t) \propto \cos(\omega t - k x)
\end{equation}
or as
\begin{equation}
\phi^-(x, t) \propto \cos(\omega t + k x)
\end{equation}
Assume that you want to focus on the $x$-position of the maximum of the wave at any given time. This can be of course generalized for a point at any phase in the wave.
The maximum occurs at phase equal to zero ($\cos(0)=1$).
the position of the maximum is at any time for a wave traveling towards the positive direction of the $x$-axis is
\begin{equation}
0 = \omega t - k x_{max} \longrightarrow x_{max}(t) = \frac{\omega}{k} t
\end{equation}
As both $k$ and $\omega$ are positive constants, we see that the position of the maximum is moving towards larger $x$-values with time (as we expect).
On the other hand, for a wave traveling towards the negative direction of the $x$-axis is
\begin{equation}
0 = \omega t + k x_{max} \longrightarrow x_{max}(t) = -\frac{\omega}{k} t
\end{equation}
Once again, as both $k$ and $\omega$ are positive constants, we see that the position of the maximum is decreasing with time.
The following is multiple choice question (with options) to answer.
The highest point of a wave is called? | [
"surge",
"threshold",
"frequency",
"crest"
] | D | Figure above also shows how the size of waves is measured. The highest point of a wave is the crest. The lowest point is the trough. The vertical distance between a crest and a trough is the height of the wave. Wave height is also called amplitude. The horizontal distance between two crests is the wavelength. Both amplitude and wavelength are measures of wave size. |
SciQ | SciQ-2081 | quantum-gravity, physical-constants
Title: What is the smallest existing thing in theory and law? What is the smallest existing thing in theory and law?
"What is the smallest existing thing in theory and law?"
The Merriam Webster Dictionary defines a "thing" as:
: an object or entity not precisely designated or capable of being
designated
a: an inanimate object distinguished from a living being
b: a separate and distinct individual quality, fact, idea, or usually
entity
c: the concrete entity as distinguished from
...
A Photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force (even when static via virtual particles). Mass: 0 < 1×10−18 eV/c^2.
The photon has zero rest mass and always moves at the speed of light within a vacuum. Since the Photon is a Point Particle and has a size of zero you might say it's not a thing, nothing; that leaves us with:
The smallest real thing is the Neutrino. Mass: ≤ 0.120 eV/c^2.
The smallest theoretical thing is the Planck Particle. Radius: 5.72947×10−35 m, Mass: 3.85763×10−8 kg.
The following is multiple choice question (with options) to answer.
What is the smallest part of an element called? | [
"nucleus",
"neutron",
"core",
"atom"
] | D | The smallest particle of an element that still has the properties of that element is the atom . Atoms actually consist of smaller particles, including protons and electrons, but these smaller particles are the same for all elements. All the atoms of an element are like one another, and are different from the atoms of all other elements. For example, the atoms of each element have a unique number of protons. |
SciQ | SciQ-2082 | tissue
Title: Tissues in plants and animals
What is the equivalent connective tissue in plants?
Connective tissue in animals are mostly made up of collagen.
What about in plants?
Connective tissue in animals are mostly made up of collagen
Tissue is not like a simple chemical mixture ; rather tissue means a group or assemblage of cells, obeying certain defining-characteristics.
Animal connective tissues contain collagen mostly in the extracellular matrix. There are also other cell-constituents like phospholipid(membranes), DNA, RNA, etc. Blood is a liquid connective tissue which do not contain collagen in its matrix (plasma)
What is the equivalent connective tissue in plants?
Connective tissue is defined as all the tissues originated from the mesoderm layer of the animal embryo.
Now plants have a different mode of development than animals (plausibly due to evolution in separate route). So no part of a plant-body is homologous with a part of animal-body. It is impossible to bring a compare.
However; plants too; have their extracellular matrix; which is more popular as plant's cell wall (that contain cellulose, hemicellulose, etc.) as well there are intercellular spaces.
Still, if you forcefully want to bring a comparison; then the ground-tissue system of plant maybe called as a rough analogy with connective tissues in animals ( Similarly epidermal tissue of plant maybe a rough analogy with epithelial tissue of animals)
The following is multiple choice question (with options) to answer.
Dermal tissue covers the outside of a plant in a single layer of cells called what? | [
"cambium layer",
"cuticle",
"scales",
"the epidermis"
] | D | Dermal tissue covers the outside of a plant in a single layer of cells called the epidermis . You can think of the epidermis as the plant’s skin. It mediates most of the interactions between a plant and its environment. Epidermal cells secrete a waxy substance called cuticle , which coats, waterproofs, and protects the above-ground parts of plants. Cuticle helps prevent water loss, abrasions, infections, and damage from toxins. |
SciQ | SciQ-2083 | blood-circulation, kidney
Title: Why does glomerulus don't allow white blood cells to leave? The glomerulus in nephrons are just a ball of capillaries, so why can't it allow the white blood cells to squeeze though the epithelial cells into Bowman's capsule just like the formation of tissue fluid in other capillaries by filtration? Red blood cells, White blood cells, platelets and proteins with large molecular weight cannot pass through the podocyte and fenestrations in glomerular capillary, but small molecules like water, salts and sugars are filtered out as part of urine.
As these cells and proteins are large to cross through this filter, they remain in the capillary and create osmotic pressure within the capillary. Bowman’s space has osmotic pressure approximately zero. So, only hydrostatic pressure works in this state and help in movement of fluid across the capillary wall.
Via: https://opentextbc.ca/anatomyandphysiology/chapter/25-5-physiology-of-urine-formation/
The following is multiple choice question (with options) to answer.
After fluid collects in nephron tubules in the kidney, where does it move to? | [
"the uterus",
"the bladder",
"the spleen",
"the prostate"
] | B | The location of nephrons in the kidney. The fluid collects in the nephron tubules and moves to the bladder through the ureter. |
SciQ | SciQ-2084 | ichthyology, vertebrates
Title: If an organism is supported only by cartilage, does it have an endoskeleton? Lamprey and sharks lack bones, but does this mean they are not classified as having an endoskelton? Does an organism need bone to be considered as having an endoskeleton? From wikipedia
An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.
Cartilage is a mineralized tissue so it counts as a skeleton from this definition. A bit further in the wikipedia article it says
The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage)
The following is multiple choice question (with options) to answer.
What are external skeletons known as? | [
"exoskins",
"exoskeletons",
"scales",
"tentacles"
] | B | By the beginning of the Paleozoic, organisms had developed shells. Shells could hold their soft tissues together. They could protect the organisms from predators and from drying out. Some organisms evolved external skeletons, called exoskeletons. Organisms with hard parts also make good fossils. Fossils from the Cambrian are much more abundant than fossils from the Precambrian. |
SciQ | SciQ-2085 | dna-sequencing, metabolism
Title: Mechanics of going from DNA sequence to metabolic network My apologies for possibly a naive question. I'm a statistics type and have been asked to assist with analysis of metabolic pathways (and networks). However, I would like to have at least a layman's understanding of how metabolic pathways/networks relate to DNA sequences. Been doing the Google for a few days and, given the results, it's clear I am not formulating the query correctly since nothing seems to be clicking.
Something that helps me understand the mechanics behind going from a string of T,A,G, and C's to a network of substrates,enzymes, and products.
Thanks in advance for your patience. The question is not too broad, just involves a fair bit of work to both do the research and compose a response. I'll do the latter, but in brief.
The strings of the four nucleotides encode genes. Sometimes these genes are broken into protein-coding portions (exons) and sometimes intervening, non-coding regions (introns). Bacteria, for example do not have introns within genes while most human genes do. The nucleotides in the protein-coding portion of the gene do just that - give instructions on how to synthesize the protein by directing which tRNAs the ribosome uses to translate the genetic code into a protein chain.
A useful phrase is protein sequence dictates protein structure and that structure dictates function. So, the proteins do things and many act as enzymes or modulators of enzyme activity. An enzyme catalyzes a biochemical reaction, lowering the activation energy to go from reactant(s) to product(s). One enzyme can be thought of as one unit within a metabolic network. A modulator might activate or deactivate an existing enzyme. A protein kinase is a good example of a modulator.
Next, string some of those enzymes together to build a pathway. A common example is glycolysis. Think of this as a chain where the output or product of enzyme A serves as input to enzyme B, whose product is the input to enzyme C, and so on. These pathways are two-way, but it is exceedingly difficult to travel from the final product all the way up such a pathway to the initial input within the confines of a biological system. Thus, the pathways in practical terms are thought of as one-way.
The following is multiple choice question (with options) to answer.
What is the name for the process where data in the genes is transferred to amino acids? | [
"generation",
"transpiration",
"translation",
"mutation"
] | C | Remember that proteins are made out of amino acids. How does the information in the gene get converted from the language of nucleotides to the language of amino acids? The process is called translation . The amino acids are placed in a specific order during translation. The order is specified by the codons in the mRNA, which is produced during transcription. As the mRNA sequence is based on the gene sequence in the DNA, the order of amino acids that makes the protein is based on the gene sequence as well. |
SciQ | SciQ-2086 | dna-sequencing, metabolism
Title: Mechanics of going from DNA sequence to metabolic network My apologies for possibly a naive question. I'm a statistics type and have been asked to assist with analysis of metabolic pathways (and networks). However, I would like to have at least a layman's understanding of how metabolic pathways/networks relate to DNA sequences. Been doing the Google for a few days and, given the results, it's clear I am not formulating the query correctly since nothing seems to be clicking.
Something that helps me understand the mechanics behind going from a string of T,A,G, and C's to a network of substrates,enzymes, and products.
Thanks in advance for your patience. The question is not too broad, just involves a fair bit of work to both do the research and compose a response. I'll do the latter, but in brief.
The strings of the four nucleotides encode genes. Sometimes these genes are broken into protein-coding portions (exons) and sometimes intervening, non-coding regions (introns). Bacteria, for example do not have introns within genes while most human genes do. The nucleotides in the protein-coding portion of the gene do just that - give instructions on how to synthesize the protein by directing which tRNAs the ribosome uses to translate the genetic code into a protein chain.
A useful phrase is protein sequence dictates protein structure and that structure dictates function. So, the proteins do things and many act as enzymes or modulators of enzyme activity. An enzyme catalyzes a biochemical reaction, lowering the activation energy to go from reactant(s) to product(s). One enzyme can be thought of as one unit within a metabolic network. A modulator might activate or deactivate an existing enzyme. A protein kinase is a good example of a modulator.
Next, string some of those enzymes together to build a pathway. A common example is glycolysis. Think of this as a chain where the output or product of enzyme A serves as input to enzyme B, whose product is the input to enzyme C, and so on. These pathways are two-way, but it is exceedingly difficult to travel from the final product all the way up such a pathway to the initial input within the confines of a biological system. Thus, the pathways in practical terms are thought of as one-way.
The following is multiple choice question (with options) to answer.
What play an important role in the modulation of the nuclear chain reaction? | [
"control rods",
"control neutrons",
"particle rods",
"radiation rods"
] | A | The control rods play an important role in the modulation of the nuclear chain reaction (usually a collision of a neutron with uranium). Each collision produces more neutrons than were present initially. If left unsupervised, the reaction would soon get out of control. Rods are commonly made of boron or a number of metals and metal alloys. The purpose of the control rods is to absorb neutrons to regulate the rate of the chain reaction so that the water does not overheat and destroy the reactor. |
SciQ | SciQ-2087 | human-biology, physiology
Title: Why should or shouldn't we allow the human body to take its natural course? For example, when you are sick but don't feel thirsty, this could be due to baroreceptor reflex that is attempting to readjust salt and water balancing.
Why shouldn't a patient be left thirsty and let the body to adjust until he or she feels thirsty again? I am assuming that your question is: "why can a human intervention improve health?". Let me know if I misunderstood your question.
Why can a human intervention improve health?
Let's first avoid going into the details of your example. It is quite obvious that human intervention can often improve health in a way that your body alone cannot. To me, an intuitive way to classify the reasons why human intervention are important to improve health into two categories.
The body does not always react in an adaptive manner.
Example: Anaphylaxis is a serious and sudden allergic reaction that may cause death. An allergic reaction is what is happening when your immune system recognize a chemical as a infectious element while it is not. The reaction of the body is not adaptive and taking medication such as an anti-histaminic can force the body to stop this "stupid" reaction.
Note: There are reasons why the body cannot be always perfect but it is a bit long to make an overview here. There is stochasticity in the developmental processes, there is genetic variation for example due to always occurring deleterious mutations, there is also an arms race between parasites and host. This arm race leads parasites to take advantage of normal host physiological pathways. There are tons of other reasons that relate to the stochasticity and to the physic and physiological constraints of evolutionary processes.
The body sometimes cannot (physical constraint) produce the action that is required to be performed to improve health.
Example: If you have an important wound, then a human-made compression can by far improve your chance of the survival. The body is not able by itself to simulate this external compression to prevent blood to exit the body through the wound.
The following is multiple choice question (with options) to answer.
What preventative measure is often delivered by injection into the arm? | [
"infection",
"anesthesia",
"medication",
"vaccine"
] | D | Figure 42.18 Vaccines are often delivered by injection into the arm. (credit: U. Navy Photographer's Mate Airman Apprentice Christopher D. Blachly). |
SciQ | SciQ-2088 | thermodynamics
You transferred from your lighter an amount of heat Q, which went into increase of ΔU of the helium and the work, which equals PΔV (conveniently P is constant by definition and equals in our case just 1 atm or 100000 Pa). You can see easily that NOT all of your heat went into work (that's possible only for isothermal process), so that internal energy U increased, which automatically means that temperature INCREASED too for an ideal gas (the quantity of atoms not changing). At the beginning of your experiment the volume of helium was Vo, and its energy according to ideal monoatomic gas laws was Uo = 3/2nRT (n- number of moles of helium, R is universal gas constant); because PVo = nRT for ideal gases you can see that Uo = 3/2PVo - that's at the start before setting the lighter. Hence the volume during the experiment went up from Vo to V, that automatically means that U went up from 3/2PVo to 3/2PV (P being constant). Which means that the new temperature of your helium will be (2/3)*(3/2PV)/(nR) = PV/(nR).
Increase in temperature will be accordingly ΔT = P(V-Vo)/(nR) or simply PΔV/(nR).
The following is multiple choice question (with options) to answer.
From observations as simple as blowing up a balloon, it is clear that increasing the amount of gas increases what else? | [
"area",
"the shift",
"every volume",
"the volume"
] | D | The combined gas law, , is true for a particular sample of gas. If any gas is added or allowed to leak out, however, the relationship is lost. In order to get a relationship that is true for any sample of gas, it is necessary to incorporate a term for the amount of gas. From observations as simple as blowing up a balloon, it is clear that increasing the amount of gas increases the volume. |
SciQ | SciQ-2089 | electromagnetism, optics, reflection, refraction
Title: Reflection from multiple thin films: accounting for lost light due to small surface area I have a problem similar to reflection of multiple thin films. I have light coming in from medium 1 and I want to find the total reflected intensity after being reflected inside 2 layers. However, I want to account for the fact that the surface area of medium 4 is smaller than the light's spot size and so some of the light is lost.
The following is multiple choice question (with options) to answer.
What is the scientific term for the amount of light reflected by a surface? | [
"reactivity",
"albedo",
"prism",
"inversion"
] | B | Albedo is the amount of light reflected by a surface. Sea ice has an albedo of .85, meaning 85% of light is reflected back from its surface (and leaves the Earth) and 15% is absorbed and stays in the Earth; ice-free water has an albedo of .07. (93% of the solar energy is absorbed. ) Thus the observed melting of sea ice could amplify the effect of global warming. |
SciQ | SciQ-2090 | molecular-biology, neurotransmitter, muscles, receptor
Is the membrane continuous along these tubules, or does the tubule just end somewhere inside the muscle fiber?
The membranes are continuous.
When the muscle is twitching... is this neurological of nature, or is it related to a molecular cause in the muscle itself?
Most things you'd call a muscle twitch are at the whole-muscle-group scale, involving the coordinated contraction of many individual motor units, so it's basically neurological.
When the muscle is cramping... I'm almost certain this arises in the muscle. What causes it? A malfunction with regard to the calcium ions?
A muscle cramp is a colloquialism for a couple of things that are quite different from each other. Overall, as with the previous question, if someone's experiencing a muscle cramp that means it's a fairly macroscopic phenomenon and it likely involves a whole group of muscle filaments, so it's neurological. Most spasms and cramps are neurologically mediated.
The connections with electrolyte balances (cramps from low sodium, potassium, magnesium, or calcium) also hint at the neurological basis because neurons act on each other (and on muscles) by forming or dissipating ion gradients. You may know that low dietary calcium can lead to muscle cramps; if this was relevant to the calcium release within the myocyte (from the sarcoplasmic reticulum) then the calcium-starved muscles wouldn't be expected to chronically contract (which requires calcium) but to chronically relax.
That being said, there's a lot of room for feedback mechanisms. So, let's say a person experiences a muscle tear; the tear is small enough that it doesn't compromise the function of the entire muscle group. In this case it's adaptive for the local damage to 'signal' to the rest of the muscle group to initiate spasm so as to stabilize the damaged structures as they're repaired. In this scenario the local damage would 'inform' a neurological (and/or endocrine) response that actually effects the spasm.
Lastly, and on a slightly different subject, what are the microlesions in the muscles that occur during strength training, and what is the overcompensation that happens?
The following is multiple choice question (with options) to answer.
What part of the muscle fibers cause shortening and contraction? | [
"myofibrils",
"collagen",
"fasciae",
"pores"
] | A | The sliding-and-shortening process occurs all along many myofibrils and in many muscle fibers. It causes the muscle fibers to shorten and the muscle to contract. |
SciQ | SciQ-2091 | electrons, atoms, orbitals
Title: How can an electron shell hold more than two electrons? The Pauli Exclusion principle states
in an atom or molecule, no two electrons can have the same four electronic quantum numbers. As an orbital can contain a maximum of only two electrons, the two electrons must have opposing spins.
So how can some electron shells have up to 6 electrons or more? Take the electron configuration of Magnesium. The 2p shell holds 6 electrons. How is this possible? Can you have multiple orbitals in a single electron shell? A "shell" is the term for all states with the same principal quantum number $n$, but in each shell there are also possible different values for the angular momentum quantum number $0\leq \ell \leq n$, the magnetic quantum number $-\ell \leq m_\ell \leq \ell$ and the spin quantum number $m_s\in\{-1/2,1/2\}$.
So for $n>1$, 6 electrons in a shell do not violate the Pauli exclusion principle.
The following is multiple choice question (with options) to answer.
How many electrons are in the hydrogen atom? | [
"one",
"three",
"two",
"five"
] | A | For the hydrogen atom, there is no problem since there is only one electron in the H atom. However, when we get to helium we see that the first three quantum numbers for the two electrons are the same: same energy level, same spherical shape. What differentiates the two helium electrons is their spin. One of the electrons has spin while the other electron has spin. So the two electrons in the 1s orbital are each unique and distinct from one another because their spins are different. This observation leads to the Pauli exclusion principle , which states that no two electrons in an atom can have the same set of four quantum numbers. The energy of the electron is specified by the principal, angular momentum, and magnetic quantum numbers. If those three numbers are identical for two electrons, the spin numbers must be different in order for the two electrons to be differentiated from one another. The two values of the spin quantum number allow each orbital to hold two electrons. The figure below shows how the electrons are indicated in a diagram. |
SciQ | SciQ-2092 | aqueous-solution, solubility
Title: Definition of "soluble" How to define "soluble" in chemistry?
For example, in 1:1 v/v, benzene does not mix with water, i.e. insoluble. Common sense.
However, in an analytical procedure, it called for making a "saturated" aqueous solution of benzene, which is about 1.5 g/L. So, benzene actually has some solubility in water.
So, my question is, is there an official definition of "soluble"? We consider if a solute is completely spread out through the solvent in the maximum possible extent, we consider the solute to be dissolved in the solvent. We can identify a solution by a few characteristics:
Solutions are uniform and have no precipitation or coagulated mass in it.
Solutions are clear, no granules or anything.
Solutions exhibit the phase of the solvent.
The following is multiple choice question (with options) to answer.
If a solution contains so much solute that its solubility limit is reached, the solution is said to be what? | [
"saturated",
"temperatures",
"carbohydrates",
"Over done"
] | A | If a solution contains so much solute that its solubility limit is reached, the solution is said to be saturated, and its concentration is known from information contained inTable 9.2 "Solubilities of Various Solutes in Water at 25°C (Except as Noted)". If a solution contains less solute than the solubility limit, it is unsaturated. Under special circumstances, more solute can be dissolved even after the normal solubility limit is reached; such solutions are called supersaturated and are not stable. If the solute is solid, excess solute can easily recrystallize. If the solute is a gas, it can bubble out of solution uncontrollably, like what happens when you shake a soda can and then immediately open it. |
SciQ | SciQ-2093 | energy, waves, superposition
Title: Superposition of waves and energy transferred A wave transfers energy. I was reading about the superposition of two waves, where the amplitudes of the two waves added up to produce a resultant wave.
So I began wondering about the energy that is now being transferred in this resultant wave. Is it the sum of energy being transferred by both waves?
Please help me understand. When two waves, propagating in a linear medium, interfere with each other, the amplitudes of individual points within the region of interference could add or subtract, but this does not affect the flow of energy.
We can show it in a simple example below:
Point A is in the region of interference and its amplitude will be affected by both waves.
Point B is beyond the region of interference and should not be affected by wave S2. This is because the amplitude at B is defined by a superposition of the two waves, i.e., it has to be the sum of S1 and S2 at point B. Since the amplitude of S2 at B is zero (or negligible), the amplitude at B is affected by S1 only.
The same could be said about all point of wave S1 beyond the region of interference. If so, we have to conclude that S2 would not affect S1 beyond the region of interference and therefore will not change the flow of energy of S1.
We could come to a similar conclusion, if we took into account that the waves don't get reflected while propagating in a uniform linear medium, which means that no energy is coming back and, therefore, it should continue moving forward, unaffected by other waves in that medium. The sound wave moving in the air will be reflected by a wall, but not by another sound wave.
The following is multiple choice question (with options) to answer.
What term describes waves that transfer energy through matter? | [
"temperature waves",
"energy currents",
"mechanical currents",
"mechanical waves"
] | D | Ocean waves are among the most impressive waves in the world. They clearly show that waves transfer energy. In the case of ocean waves, energy is transferred through matter. But some waves, called electromagnetic waves, can transfer energy without traveling through matter. These waves can travel through space. You can read more about electromagnetic waves in the chapter "Electromagnetic Radiation. " Waves that transfer energy through matter are the focus of the present chapter. These waves are called mechanical waves. |
SciQ | SciQ-2094 | audio, signal-synthesis, frequency-modulation
time += time_per_sample;
}
I'm currently not scaling beta with modulator frequency, if that matters.
In FM synthesis, how do I change the modulator frequency while a sound is playing without clicks or pops? If you change modulator frequency, do note that it changes a sudden jump in phase, as it changes the result of the equation where the phase is calculated from frequency. This is largely unnecessary, as having a certain frequency means the phase change is constant per sample. Thus, if you change the frequency to be a phase increment per sample, then changing the frequency does not cause a sudden phase jump but just changes the phase increment from that point on. That's how FM synth chips work.
The following is multiple choice question (with options) to answer.
What is the name of the mechanism in which sounds are encoded in microwaves by changing their frequency? | [
"molecular modulation",
"shape modulation",
"frequency modulation",
"mechanical modulation"
] | C | Cell phone signals are carried through the air as microwaves. You can see how this works in the Figure below . A cell phone encodes the sounds of the caller’s voice in microwaves by changing the frequency of the waves. This is called frequency modulation. The encoded microwaves are then sent from the phone through the air to a cell tower. From the cell tower, the waves travel to a switching center. From there they go to another cell tower and from the tower to the receiver of the person being called. The receiver changes the encoded microwaves back to sounds. |
SciQ | SciQ-2095 | botany, microbiology, terminology, etymology
Title: Rhizosphere vs. Endorhiza? In relation to microbiology and the naming of the various areas of the plant as it relates to microbial inhabitance, I am confused as to the difference between the terms endorhiza and rhizosphere.
In this case I see rhizosphere referred simply to as the 'roots', but in this case I also see endorhiza explained simply as 'roots' also.
However in this case, I see a further explanation for endorhiza (which does make sense etymologically): 'internal root tissues'.
Does this mean endorhiza is be a sub-term for the area inside the roots, and the larger area of the rhizome in general represented by rhizosphere, and that is the difference? Healthy plant growth depends on a microbial community that lives around and inside the roots of plants (Bais et al. 2001). Roots secrete from the roots a number of chemical compounds that influences the microbial community around but outside of the roots. The microbial community can include bacteria, fungi, and single-celled parasites, as well as larger organisms like insect larvae and even roots from other plants. Some chemicals attract certain organisms while other chemicals repel organisms. This community of organisms around the roots is called the rhizosphere (Walker et al. 2003). The paper by Walker (open access) describes some of the many types of symbiotic relationships that occur in the rhizosphere.
Endorhiza refers to the internal environment of the root system. The endorhiza contains another microbial community of bacteria and fungi (Backman and Sikora 2008). The organisms of this endorhizal community are collectively called endophytes. Like the rhizosphere, the organisms in the endorhiza are important symbiotic species that benefit the health of the plant.
Similar communities have been identified for other regions of the plant, such as the phyllosphere, the organisms that live on the leaves, stems and other plant parts above the ground (Backman and Sikora 2008).
The following is multiple choice question (with options) to answer.
Grasses such as wheat, rice, and corn are examples of fibrous root systems. fibrous root systems are found in monocots; tap root systems are found in these? | [
"mosses",
"dicots",
"gymnosperms",
"monocots"
] | B | has a single main root that grows down. A fibrous root system forms a dense network of roots that is closer to the soil surface. An example of a tap root system is a carrot. Grasses such as wheat, rice, and corn are examples of fibrous root systems. Fibrous root systems are found in monocots; tap root systems are found in dicots. 37 Monocots have leaves with parallel venation, and dicots have leaves with reticulate, net-like venation. 39 The process of bulk flow moves water up the xylem and moves photosynthates (solutes) up and down the phloem. 41 Gravitropism will allow roots to dig deep into the soil to find water and minerals, whereas the seedling will grow towards light to enable photosynthesis. 43 To prevent further entry of pathogens, stomata close, even if they restrict entry of CO2. Some pathogens secrete virulence factors that inhibit the closing of stomata. Abscisic acid is the stress hormone responsible for inducing closing of stomata. |
SciQ | SciQ-2096 | human-genetics
Title: In our 23 chromosome pairs, do the 2 members of the pair have distinct or virtually identical sequences? I understand that we have 46 DNA molecules in the nucleus of our cells, arranged in 23 pairs: 22 autosomal and 1 sex chromosome pairs.
I have read in different sources that the pairs contain nearly identical members, excluding any mutations. I have also read that the pairs contain 1 member we inherited from our mothers and 1 we inherited from our fathers, which are different due to inheritance.
This seems contradictory, given that genealogical companies match up on the differences on these chromosomes.
My understanding was that meiosis creates sperm and egg cells that each carry 23 chromosomes - they are haploids. During the first steps of meiosis that creates the reproductive cells we have a combining of the parent's chromosome pair from their parents to create 4 daughter cells, each independently viable, where the recombination of the chromosome pair has occurred at somewhat predictable spots (for you perhaps :-) ) and that these spots can be related to genes. It is this step that give us our genetic variation between siblings for example. A new person's DNA is partially formed from any one of these highly varied daughter cell possibilities.
Fertilization combines the reproductive cells to produce the 46 chromosome zygote with is again diploid.
I think this understanding supports the second interpretation that our chromosome pairs are not 2 nearly identical DNA molecules but are distinct.
Have I got this right? Is there a missing process or a misunderstanding in my interpretation? Homologous chromosomes (those that are paired up), excluding the sex pair are almost identical in size, shape and genes (members as you called them) present in them.
Genes determine traits and each homologous chromosome controls the same traits. The level of identity of a gene inside a population varies between genes. There are very conserved ones that do not change even between humans and yeast and others that vary alot event inside a species. This changes can be small in sequence length, a simple base (letter) swap or one deletion, and have a huge effect on the traits. This is how chimps and humans are very different but share 98.6% of their genome and humans are very similar and share 99.9% of their genome.
In summary, on the bigger scale homologous chromosomes are very similar (size, shape, traits inside), on the smaller scale homologous chromosomes have small changes that affect greatly.
The following is multiple choice question (with options) to answer.
Humans have about 20,000 to 22,000 genes scattered among 23 of these? | [
"ribosomes",
"atoms",
"neutrons",
"chromosomes"
] | D | The nucleus is a membrane-enclosed organelle found in most eukaryotic cells. The nucleus is the largest organelle in the cell and contains most of the cell's genetic information (mitochondria also contain DNA, called mitochondrial DNA, but it makes up just a small percentage of the cell’s overall DNA content). The genetic information, which contains the information for the structure and function of the organism, is found encoded in DNA in the form of genes. A gene is a short segment of DNA that contains information to encode an RNA molecule or a protein strand. DNA in the nucleus is organized in long linear strands that are attached to different proteins. These proteins help the DNA to coil up for better storage in the nucleus. Think how a string gets tightly coiled up if you twist one end while holding the other end. These long strands of coiled-up DNA and proteins are called chromosomes. Each chromosome contains many genes. Humans have about 20,000 to 22,000 genes scattered among 23 chromosomes. |
SciQ | SciQ-2097 | geology, paleontology, dating, history-of-science
Title: Did geologists determine the age of rocks and fossils before the advent of modern scientific dating methods? Did geologists determine the age of rocks and fossils before the advent of modern scientific dating methods such as radiometric, electron spin resonance and thermoluminescence?
If they did, does anyone know how they went about it? The approach adopted by Charles Lyell (and other writers in a similar timeframe), in his book 'Principles of Geology' which was first published in the 1830s was to look at processes in the modern landscape where the rate of change could be determined by observation or from historical evidence, and assuming that similar processes operated at similar rates in the geological past. So, for instance, if you measure the amount of sediment transported by a river today, and you measure the volume of sediment in that river's delta, you can estimate how long that delta took to form. If you see a similar delta in the geological record, you can assume it took a similar time to form. Lyell's estimates of the age of the earth were low, but as the concept of plate tectonics, with it's progressive recycling of rocks through subduction wasn't recognised, it was remarkably prescient.
The following is multiple choice question (with options) to answer.
What is the term for the use of radioactive decay to estimate the ages of fossils and rock? | [
"isotope test",
"radioactive illustrating",
"microwave theory",
"radioactive dating"
] | D | Radioactive dating is the use of radioactive decay to estimate the ages of fossils and rocks. An example is carbon-14 dating. |
SciQ | SciQ-2098 | volcanology, volcanic-hazard
Title: How long will red hot lava from the Sundhnúkur eruption in Iceland be visible? I'll be in Iceland in a few weeks and would love to see glowing red hot lava, however, the recent Sundhnúkur eruption just ended, after erupting for three days. So no new lava is being pumped out, I guess, but I imagine it'll take the lava that's already come out some time to cool.
My question is... how long will it take for the lava to cool such that it's not glowing red? I have experienced a similar situation two years ago. I visited the site of the 2021 Fagradalsfjall eruption on November 18, 2021, exactly two months after the last emission of lava (and one month before the Icelandic Met Office declared the eruption officially over on December 18). We walked on top of the solidified crust of the lava pond to reach the main vent (don't do it, see below). There were some fissures in the crust, like this one, about 20 cm wide:
And if you looked inside the fissure, you could actually see some red glowing lava at the bottom, maybe 3 meters deep:
Nothing impressive, and maybe not what you had in mind, but it definitely qualifies as "red hot lava", two months after the magma supply had ended. That being said, here are some thoughts about your trip plans:
The eruption may be over, but the area is still closed for the time being. Here is the current hazard map, valid until December 29 (check for updates to see how the situation evolve).
Compared to other countries, Icelanders usually have very relaxed
rules regarding access to eruption sites (the freedom to access
private lands is a cultural thing called almannaréttur and is even
written in law). So if the access is forbidden, it means Iceland
authorities have very good reasons to do it.
Indeed, there is still ground inflation measured in the area, below the Svartsengi geothermal plant. It means that magma accumulation has resumed and another eruption is already on its way, although it could take weeks or months. It could be during your stay if you're lucky—and if access is allowed...
The following is multiple choice question (with options) to answer.
On which ridge does iceland sit? | [
"Pacific rim",
"Arctic circle",
"Antarctic ridge",
"mid-atlantic ridge"
] | D | Most mid-ocean ridges are located deep below the sea. The island of Iceland sits right on the Mid-Atlantic ridge ( Figure below ). |
SciQ | SciQ-2099 | organic-chemistry
Title: How did early chemists determine the major product of a solution? For example, how did they determine using evidence that when 2-chloropropane reacted with ethoxide, a strong base, formed propene as the major product and 2-ethoxypropane as the minor product?
Could someone explain how did chemists determine the major products without NMR Spectroscopy? I have no lab experience and do not have access to them either. In absence of currently available (or, in principle available) spectroscopies like NMR, IR, Raman, UV-Vis; and mass spectrometry our ancestors tried first to separate the products obtained by sequential recrystallisation. Or by extraction under acidic, neutral, basic conditions (including back extraction).
They then recorded other physical properties of the purified products, if accessible, which then were compared with reference data. For example, melting point and crystal shape if the products were solid, otherwise boiling point, refractive indices of the products obtained. Then, they knew a whole array of pretests to check for the presence / absence of elements in the products formed, like Beilstein test for halogens and Lasaigne test for nitrogen. They would determine the molecular weight by means of cryoscopy or ebullioscopy.
From a chemical point of view, it was common to subject the products to combustion analysis to determine the molecular formula. (One of the instruments for this, the Kaliapparat is still present in the logo of The American Chemical Society.) Till today, there are journals preferring this over a mass spectroscopic determination of the molecular weight.
They knew about reactions that would yield derivatives, for example from the reaction with picric acid (affording pircrates), or with toluenesulfonic acid (yielding amides); often crystalline with a sharp melting point, easing to compare with reference data. If not, other reactions like the haloform reaction would sequentially degrade the products into fragments, and then these products obtained would be characterised by physical or chemical means.
And obviously, the balance was much more "sacred" than today, where often we "just" weight-in reactants, and weight-out products.
The following is multiple choice question (with options) to answer.
How are the major families of organic compounds characterized? | [
"their thermal groups",
"Their optic groups",
"their visual groups",
"their functional groups"
] | D | In Chapter 2 "Molecules, Ions, and Chemical Formulas" and Chapter 5 "Energy Changes in Chemical Reactions", you were introduced to several structural units that chemists use to classify organic compounds and predict their reactivities. Thesefunctional groups, which determine the chemical reactivity of a molecule under a given set of conditions, can consist of a single atom (such as Cl) or a group of atoms (such as CO2H). The major families of organic compounds are characterized by their functional groups. Figure 24.1 "Major Classes of Organic Compounds" summarizes five families introduced in earlier chapters, gives examples of compounds that contain each functional group, and lists the suffix or prefix used in the systematic nomenclature of compounds that contain each functional group. |
SciQ | SciQ-2100 | biochemistry, biophysics, bioenergetics
Title: Are there known life forms that are able to transform mechanical energy into chemical energy? Are there known life forms that are able to transform mechanical energy into chemical energy?
This question asks a similar subject, but more specific and has no answers.
The background of this question are thoughts about hypothetical life on tidally locked exoplanets of red dwarf stars, where light for photosynthesis is scarce but mechanical energy (storms and/or water currents) aplenty. There are no known life forms that use mechanical energy as a primary form of metabolic energy (i.e., for generic cellular functions). Many life forms are sensitive to mechanical disruption in some way, so they do utilize mechanical energy, but in a very limited fashion (@David's answer touches on this), and of course many organisms have life cycles that somehow depend on mechanical transportation (seed/spore dispersal, traveling on the wind or ocean currents, etc).
I think the main physical problem is that mechanical energy just isn't available to biological cells in a form that can be converted to substantial chemical energy. They are small, and tend to have other great benefits for being small.
To use an ocean wave as an example, there is very little or no perceptible movement for a cell in that wave, besides an apparent increase and decrease in the force of gravity. The top and bottom of the cell are moving together with the flow of water, so there is no differential to operate on.
An E. coli weighs about 1 picogram. If it could capture all of the energy from falling from 1km in the air on earth, assuming no uncaptured aerodynamic drag, that would be about 10-11 joules.
If there are ~3000 kJ/mol of energy available from burning glucose, that means about 5 × 10-21 joules per molecule of glucose, so about 20 billion glucose molecules, which sounds like a lot but it is only 1 femtogram, 0.1% the weight of the cell.
The following is multiple choice question (with options) to answer.
What do chemotrophs extract energy from? | [
"chemical compounds",
"carbon compounds",
"fatty compounds",
"liquid compounds"
] | A | A living cell is a system that is not in equilibrium with its surroundings; it requires a constant input of energy to maintain its nonequilibrium state. Cells maintain a low-entropy state by increasing the entropy of their surroundings. Aerobic organisms cannot survive in the absence of O2, whereas anaerobic organisms can live only in the absence of O2. Green plants and algae are phototrophs, which extract energy from the environment through a process called photosynthesis, the photochemical reduction of CO2 to a reduced carbon compound. Other species, called chemotrophs, extract energy from chemical compounds. One of the main processes chemotrophs use to obtain energy is respiration, which is the reverse of photosynthesis. Alternatively, some chemotrophs obtain energy byfermentation, in which an organic compound is both the oxidant and the reductant. Intermediates used by organisms to shuttle electrons between the reductant and the oxidant include NAD+ and NADH. Energy from the oxidation of nutrients is made available to cells through the synthesis of ATP, the energy currency of the cell. Its energy is used by cells to synthesize substances through coupled reactions and to perform work. The body stores energy as sugars, protein, or fats before using it to produce ATP. |
SciQ | SciQ-2101 | is the same) and the area is [pi]/2*(R 2-r 2). The centroid of the planar curve can be determined by a single integration through sweeping the elemental centroid of the curve fragment along variable angle c circularly. Radii of gyration iy, iz. (In other words, if you made the triangle out of cardboard, and put its centroid on your finger, it would balance. The centroid coincides with the center of mass or the center of gravity only if the material of the body is homogenous (density or specific weight is constant throughout the body). Right Click the X field and click the Calculate Geometry. Quick guide to geometry generator symbol layers. The complexity of the finite element approach is hidden. MATH 30 FORMULA SHEET Triangles c a b 45 ¡ 45 ¡. Centroid of semi-circle is at a distance of 4R/3π. The angle between the axis connecting the centroid of the optic disc and the foveal center and the horizon, called the disc–fovea angle (DFA), is an anatomical parameter that has been found to affect the RNFL course toward the optic disc. Also known as the centroid. CLASS X FORMULAE MATHS Median The median for the grouped data can be found by using the formula: Median =!+!!!!"! ×ℎ l = lower limit of the median class. ) A = bt tb3 sin2 /3 12 tb3 cos2 (3 12 tb3 sin2 (3 — Regular polygon with n sides (Origin of axes at centroid) centroid (at center of polygon) number of sides (n 3) = central angle for a side length of a side interior angle (or vertex angle). 5 By integral formula. Even Numbers (Integers) Odd Numbers (Integers) Divisibility Rules. The region bounded by y = 3−e−x. Jumping right in:. If the angle is 180 degrees then the sector is a semi-circle. Hence, the centroid is given by. Circle Sector Calculator This is an example of doing multiple math calculations to come to a series of results. index: click on a letter : A: B: C: D: E: F: G: H: I : J: K: L: M: N: O: P: Q: R: S: T: U:
The following is multiple choice question (with options) to answer.
Involved in balance, the semicircular canals are parts of what organs? | [
"ovaries",
"eyes",
"ears",
"lungs"
] | C | The parts of the ears involved in balance are the semicircular canals. These are the curved structures above the cochlea in the inner ear in Figure above . Like the cochlea, the semicircular canals contain liquid and are lined with tiny hair cells. As the head changes position, the liquid moves. This causes the hair cells to bend. The bending of the hair cells triggers nerve impulses that travel to the cerebellum in the brain. The cerebellum uses the information to maintain balance. |
SciQ | SciQ-2102 | newtonian-mechanics, forces, rotational-dynamics, torque
Title: Falling off a chair, how best to save yourself If I consider a man sitting on an office chair that reclines backwards iff you lean backwards.
What could be done to prevent hin from falling?
a) raising his legs till they are parallel to ground.
b) bring the feet closer to himself(as close as possible) and press them down on the ground.
Please don't suggest any other way. I want to compare these two. Ie, which is better.
Argument in favor of a)
The center of mass moves away from the rear end of the chair towards the forward end of the chair so torque of weight will restore the chair. (This works if you are in an armchair, and are rocking to and fro).
However, intuition says contrary to this. I feel scared of falling If I do this.
Argument in favour of b)
Intuition favours this. Normally when we talk about balancing our body, what "feels right" is better for the safety. So, I can not say what is right. Please explain what your views are in this case. Again, the purpose of this question is not to ask what should be done, only what is better to do out of these two choices. This sounds to me like an experimental question (but be careful not to hurt yourself!).
Note that since you want the chair to rotate forwards towards the ground, you'll want to consider the direction of the angular momentum your motion introduces. If you kick your legs out rapidly, not only does the weight of your feet tilt the chair forward, but the angular momentum of your legs moving upwards in front of the chair will tend to be balanced by an upward motion of the back of the chair. However, if you're tilted too far backwards before you kick out your legs, you'll get a second and opposite angular momentum kick once your knees are straight, which might send you over backwards.
This is why the best approach is to stick out your legs and pinwheel your arms.
The following is multiple choice question (with options) to answer.
Injuries can be prevented by getting proper what? | [
"drugs and food",
"exercise and training",
"water and clothing",
"rest and recovery"
] | D | Injuries can also be prevented by proper rest and recovery. If you do not get enough rest, your body will become injured and will not react well to exercise, or improve. You can also rest by doing a different activity. For example, if you run, you can rest your running muscles and joints by swimming. |
SciQ | SciQ-2103 | botany, terminology, fruit
Title: What is the name of this part in plants, fruits, vegetables? What is the name of this part of the plant, fruit, vegetable? The thing that the plant is connected with the tree and gets nutrients with? The part we usually cut out when eat fruit.
Examples below
Papaya
Banana
Mango 'Stalk' or 'pedicel' would be an appropriate term (see, for example, this paper or this one). Specifically, you could say 'terminal part of the stalk/pedicel', though I don't know if there is a word for that.
Note that the term pedicel is commonly used for the stalk of a flower; it makes sense to use it for fruits too as they are derived from flowers.
The following is multiple choice question (with options) to answer.
Some leaves are attached to the plant stem by a petiole. leaves that do not have a petiole and are directly attached to the plant stem are called this? | [
"sheath leaves",
"globular leaves",
"transverse leaves",
"sessile leaves"
] | D | Structure of a Typical Leaf Each leaf typically has a leaf blade called the lamina, which is also the widest part of the leaf. Some leaves are attached to the plant stem by a petiole. Leaves that do not have a petiole and are directly attached to the plant stem are called sessile leaves. Small green appendages usually found at the base of the petiole are known as stipules. Most leaves have a midrib, which travels the length of the leaf and branches to each side to produce veins of vascular tissue. The edge of the leaf is called the margin. Figure 30.21 shows the structure of a typical eudicot leaf. |
SciQ | SciQ-2104 | humidity, water-vapour
Title: Water vapor content versus specific humidity I am wondering the difference between water vapor content and specific humidity to determine the moisture availability in the atmosphere. Which one is more acceptable variable to determine the moisture availability in the atmosphere?
I need to show the moisture availability in the atmosphere in my study. So should I explain it through water vapor content or through specific humidity? I will explain the rainfall deficiency over a region For a study relating to rainfall, I would be inclined to look at total column water vapour (TCWV), also known as integrated water vapour (IWV) or precipitable water. They're all (more or less) the same thing.
The company Remote Sensing Systems describes it as:
Total column water vapor is a measure of the total gaseous water contained in a vertical column of atmosphere. It is quite different from the more familiar relative humidity, which is the amount of water vapor in air relative to the amount of water vapor the air is capable of holding. Atmospheric water vapor is the absolute amount of water dissolved in air. When measured in linear units (millimeters, mm), it is the height (or depth) the water would occupy if the vapor were condensed into liquid and spread evenly across the column. Using the density of water, we can also report water vapor in kg/m2 = 1 mm or g/cm2 = 10 mm.
For rain to form, clouds need to form first. Clouds need cloud condensation nuclei, but crucially, for clouds to form, the water vapour partial pressure needs to reach the saturation vapour pressure. The latter is strongly dependent on temperature (Clausius-Clapeyron relation), so a profile of relative humidity is not the most directly useful quantity. The total column water vapour describes how much liquid water might form, which is why it is sometimes even described as precipitable water.
You can get this product either from reanalysis (like ERA-5) or retrieved from hyperspectral infrared sounders, such as IASI, AIRS, or CrIS. Depending on where and when in the world you're looking at, there may also exist products from geostationary instruments.
The following is multiple choice question (with options) to answer.
What is water vapor density known as? | [
"ambiance",
"thickness",
"humidity",
"density"
] | C | saturation vapor density given in the table. Strategy To solve this problem, we need to break it down into a two steps. The partial pressure follows the ideal gas law,. |
SciQ | SciQ-2105 | thermal-radiation, heat-conduction, radiative-transfer
Title: Is thermal conduction really radiation? I have no doubt thermal conduction is a useful model for heat transfer, wherein kinetic energy is transferred between particles when they collide. However, according to explanations that I believe are canonical, two molecules collide due to electromagnetic repulsion (and possibly Pauli Exclusion) of their electron "clouds". In the standard model of particle physics, electromagnetic repulsions between electrons occur via the exchange of force-carrying particles, which happen to be photons. (Virtual photons, if I'm not mistaken, and perhaps that is an important point here.)
So, if thermal conduction is microscopic kinetic energy transfer due to molecular collisions, and molecular collisions occur by the exchange of photons, then it appears to me that at a fundamental level thermal conduction is a special case of energy transfer by photons, which in my understanding, is the radiation mechanism of heat transfer.
Is this conclusion incorrect (and if so, why)? The important distinction between thermal conduction and thermal radiation is that the heat exchange is driven by the difference in temperature for thermal conduction and the heat exchange is driven by the fourth power of the difference in temperature for thermal radiation. Perhaps it would be possible to derive, on a microscopic level, the relationship between this fourth-power microscopic radiation and the macroscopic first-power conduction equation. However, I am not aware of such a derivation and it is not immediately obvious. Certainly, even if such a microscopic derivation is possible, the macroscopic form is sufficiently different to warrant its own category
The following is multiple choice question (with options) to answer.
What is the name for the transfer of thermal energy between particles of matter that are touching? | [
"conduction",
"induction",
"activation",
"convection"
] | A | Conduction is the transfer of thermal energy between particles of matter that are touching. Thermal conduction occurs when particles of warmer matter bump into particles of cooler matter and transfer some of their thermal energy to the cooler particles. Conduction is usually faster in certain solids and liquids than in gases. Materials that are good conductors of thermal energy are called thermal conductors . Metals are especially good thermal conductors because they have freely moving electrons that can transfer thermal energy quickly and easily. |
SciQ | SciQ-2106 | kinetic-theory, mean-free-path
Title: Mean free path of gas mixture I come cross a question about calculate the MFP of a gas mixture, which contains several different kinds of molecules, each has different size, velocity and number density. My question is: How can I calculate the MFP of a mixture like this. Let's assume each component of the mixture follows the ideal gas law. Below is educated guesswork. Someone more informed about statistical mechanics can perhaps do a better job.
The mean free path is usually estimated by employing following argument for a dilute gas. Suppose number density of gas molecules is $n$, and each has diameter $d$. Then collision cross-section of a molecule is $\pi d^2$. If a molecule moves a distance $l$ then the volume swept out by the collision cross section is $\pi d^2l$. For collision to occur there must be 1 molecule in this swept volume, i.e. $n\pi d^2l\sim 1$ which gives $l\sim (n\pi d^2)^{-1}$, where $l$ is now interpreted as the mean free path. All of this is standard stuff, and more rigorous expressions for mean free path can perhaps be derived. However let us build on this simple argument to get an estimate of mean free path in a mixture of gases.
Suppose there are $N$ species in the gas mixture, which we shall label using numbers $1$ through to $N$. Let $n_i$ be the number concentration of species $i$. Therefore the probability that a randomly picked molecule is of species $i$ is $P_i=n_i/(\sum_kn_k)$.
The following is multiple choice question (with options) to answer.
The mean free path for a gaseous molecule will be hundreds of times the what of the molecule? | [
"weight",
"density",
"variation",
"diameter"
] | D | If you have ever been in a room when a piping hot pizza was delivered, you have been made aware of the fact that gaseous molecules can quickly spread throughout a room, as evidenced by the pleasant aroma that soon reaches your nose. Although gaseous molecules travel at tremendous speeds (hundreds of meters per second), they collide with other gaseous molecules and travel in many different directions before reaching the desired target. At room temperature, a gaseous molecule will experience billions of collisions per second. The mean free path is the average distance a molecule travels between collisions. The mean free path increases with decreasing pressure; in general, the mean free path for a gaseous molecule will be hundreds of times the diameter of the molecule In general, we know that when a sample of gas is introduced to one part of a closed container, its molecules very quickly disperse throughout the container; this process by which molecules disperse in space in response to differences in concentration is called diffusion (shown in Figure 9.27). The gaseous atoms or molecules are, of course, unaware of any concentration gradient, they simply move randomly—regions of higher concentration have more particles than regions of lower concentrations, and so a net movement of species from high to low concentration areas takes place. In a closed environment, diffusion will ultimately result in equal concentrations of gas throughout, as depicted in Figure 9.27. The gaseous atoms and molecules continue to move, but since their concentrations are the same in both bulbs, the rates of transfer between the bulbs are equal (no net transfer of molecules occurs). |
SciQ | SciQ-2107 | climate-change, geothermal-heat, crust, thermodynamics, fossil-fuel
Title: Do fossil fuels insulate the crust from the Earth's interior? I was doing a project for my English class, and I came upon the article Energy conservation in the earth's crust and climate change. I can't view the full text of the article, but the abstract piqued my interest:
Do long hydrocarbons in the earth actually have a significant effect in insulating the surface? Also, has the lack of these hydrocarbons resulted in any significant warming of the Earth thus far? Quoting from John Russell's response to this article, "This is arrant nonsense!"
Russell concludes with
How did this paper get through the peer-review and editorial review processes? What technical standards were applied to determine the apparent merit of its contents so as to justify its inclusion in a reputable journal?
Just because something is published in a scientific journal does not mean it is fact. Publication is where science starts rather than ends. Sometimes, pure garbage manages to slip through peer review and get published, even in reputable journals. This is one of those times. Moreover, the publisher of the underlying journal, Taylor & Francis, has had issues with shoddy peer review.
The Earth's energy imbalance is 0.6±0.17 W/m2. The Earth's internal energy budget, the amount of energy that escapes from the interior of the Earth, is 0.087 W/m2, about half the uncertainty in the Earth's energy imbalance. (That largish uncertainty is because the imbalance is a difficult quantity to measure.) Even if all of that 0.087 W/m2 is due to humans removing the Earth's insulating layer of hydrocarbons (it isn't), it does not come close to accounting for the 0.6±0.17 W/m2 imbalance. The numbers don't add up.
Or as John Russell put it in his response to the referenced article, "This is arrant nonsense!"
The following is multiple choice question (with options) to answer.
What is the most common fossil fuel? | [
"uranium",
"coal",
"methane",
"diesel oil"
] | B | Many of the problems with fossil fuels are worse for coal than for oil or natural gas. Burning coal releases more carbon dioxide than either oil or natural gas. Yet coal is the most common fossil fuel, so we continue to burn large amounts of it. That makes coal the biggest contributor to global warming. |
SciQ | SciQ-2108 | climate-change, climate
In this case, as it is an area that it is almost constantly cloudy with high humidity, temperature is varying just a little bit, and except the first day of the period, it seems that there is no relationship. In fact, on the second day there was a storm (I am living now at Singapore) and it is reflected in a quick change in temperature (both) and solar radiation.
Conclusion: It is not as simple as it seems.
Hope it helps!
The following is multiple choice question (with options) to answer.
The weather conditions in an area over time is also called a what? | [
"climate",
"landscape",
"biome",
"habitat"
] | A | |
SciQ | SciQ-2109 | organic-chemistry, nomenclature, notation
Title: Symbol to denote a group which is either an oxygen atom or NH group I'm drawing the generic structure of several different organic molecules in my thesis. They share some features, one of which is a carbonyl carbon attached to either an oxygen atom (i.e. ester) or an $\ce{-NH}$ (i.e. amide).
My first instinct was to draw it like this†: $\ce{R-X-C(=O)-R'}$
But I wonder if X wrongly implies that it's a halogen? In which case, what would be the correct letter or symbol to use? I've seen Z used sometimes when X is used elsewhere, would that be more appropriate? Or perhaps Q for heteroatom, as in Reaxys? Or A for 'any'?
† I'm actually drawing in ChemDraw, this is simplified for the sake of the question
Edit: corrected mistake (nitrogen atom -> $\ce{-NH}$ group) Oxygen and nitrogen have different valencies, so you can't use the same letter to denote literally an $\ce{O}$ or an $\ce{N}$ atom, as they can't be directly substituted for one another.
You should use the same letter to denote $\ce{O}$ or $\ce{NH}$, for example. It's perfectly permissible to write $\ce{R-X-C(O)-R'}$ and say $\ce{X} = \ce{O}, \ce{NH}$. This approach is commonly used in the literature. If your amide is tertiary then write something like $\ce{X} = \ce{O}, \ce{NH}, \ce{NR}$. The same applies to structures drawn in ChemDraw.
Beyond that, the choice of letter is arbitrary (as long as you define it!) so $\ce{X}$ is perfectly fine, although you should obviously avoid letters which already represent a chemical element (e.g. $\ce{B}$, $\ce{C}$, ...).
The following is multiple choice question (with options) to answer.
Chemical symbols are useful to concisely represent the elements present in a substance. the letters usually come from the name of what? | [
"element",
"month",
"discoverer",
"scientist"
] | A | Chemical symbols are useful to concisely represent the elements present in a substance. The letters usually come from the name of the element. |
SciQ | SciQ-2110 | cell-biology, molecular-biology
Title: Intracellular lipid transport I know that lipids are carried around the body in the blood either as micelles or by lipid-binding proteins which allow them to be solved.
Lipids can't always be integrated in a membrane though, the phospholipids used in membranes have to be synthesised somewhere from a precursor which will also by hydrophobic.
Consequently, at some point there will have to be transport of lipids within the cell where the lipids will need to be in solution. How is this facilitated? Like in the blood, intracellular lipid trafficking is facilitated by vesicular transport and lipid carriers like fatty acid binding proteins. In addition, intracellular membranes are densely packed and they can exchange lipids by collision and transient hemifusion. If you have access to Cell, a good review is from Prinz W. 2010 Lipid Trafficking sans vesicles, Where, Why, How?
The following is multiple choice question (with options) to answer.
Cell transport refers to the movement of substances across what structure? | [
"cell membrane",
"chloroplasm",
"cell wall",
"phloem"
] | A | Cell transport refers to the movement of substances across the cell membrane. Probably the most important feature of a cell’s phospholipid membranes is that they are selectively permeable. A membrane that is selectively permeable , or semipermeable, has control over what molecules or ions can enter or leave the cell, as shown in Figure below . This feature allows a cell to control the transport of materials, as dictated by the cell's function. The permeability of a membrane is dependent on the organization and characteristics of the membrane lipids and proteins. In this way, cell membranes help maintain a state of homeostasis within cells (and tissues, organs, and organ systems) so that an organism can stay alive and healthy. |
SciQ | SciQ-2111 | electromagnetism, energy, definition
Title: Dependence of current in electronvolts Definition: 1 eV is when an electron passes through a potential difference of 1 V and gains/loses energy.
Where is this potential difference? Is it between two plates in a apparatus setup?
Is this potential difference and applied voltage to the experimental setup/circuit, are they two different things?
If the device used to create a potential difference of 1 V used a power of 1 watt and 1 ampere current, then can we define 1 eV as being the energy gained by electron when it passes through a electric field using 1 watt power using 1 ampere current?
I am not sure if my third question makes sense. If you could help me with corrections or clarification, that would be great. Your definition is not accurate. One electron-volt is an energy unit equivalent to the amount of energy gained (or lost) by one electron accelerated across a potential difference of 1 V. What you have stated is simply a result of the acceleration, not the definition of the electron-volt. Plus, we should be even more general and instead of using the electron, we should use a particle with a charge of 1 electronic unit, e.
The acceleration of an actual electron doesn't have to happen. Nor does there actually have to be a potential difference. Those are merely concrete items which are used to define an equivalent amount of energy. The mass energy of an electron is approximately 511,000 electron volts, but there doesn't have to be any potential of 511,000 volts for the electron to exist.
The following is multiple choice question (with options) to answer.
What term describes the rate at which a device changes electric current to another form of energy? | [
"electric power",
"kinetic energy",
"kilowatts",
"voltage"
] | A | The rate at which a device changes electric current to another form of energy is called electric power . The SI unit of power—including electric power—is the watt. A watt equals 1 joule of energy per second. High wattages are often expressed in kilowatts, where 1 kilowatt equals 1000 watts. The power of an electric device, such as a microwave, can be calculated if you know the current and voltage of the circuit. This equation shows how power, current, and voltage are related:. |
SciQ | SciQ-2112 | quantum-mechanics, newtonian-mechanics
Title: What happens to a radioactive element or isotope's electrons when it undergoes alpha decay? It seems to make sense that when an atom loses two protons, it would lose two electrons as well, but I don't actually know what happens. It is complicated and we ignore it, but your intuition is right. When the nucleus loses an alpha particle its charge decreases by two. The atomic physicists now claim their job is done and don't care. The solid state physicists don't consider radioactivity, so they don't care either. If it is an atom floating freely in space, two electrons will move off in some direction, but who cares? If it is an atom in a solid crystal, you should ask how much the recoil moves the atom and whether it dislocates the crystal.
The following is multiple choice question (with options) to answer.
What happens when a sodium atom loses an electron? | [
"gains a proton",
"becomes sodium ion",
"becomes calcium",
"combines with hydrogen"
] | B | By losing an electron, the sodium atom becomes a sodium ion. It now has one less electron than protons, giving it a charge of +1. Positive ions such as sodium are given the same name as the element. The chemical symbol has a plus sign to distinguish the ion from an atom of the element. The symbol for a sodium ion is Na + . |
SciQ | SciQ-2113 | electrostatics
http://en.wikipedia.org/wiki/Electronegativity#Electronegativities_of_the_elements
The redder atom, the higher electronegativity, and the more likely it is for the atom to gain electrons and become negatively charged. That's especially true for light halogens (fluorine, chlorine) and oxygen. That's partly why glass - with lots of $SiO_2$ - likes to get negatively charged in the triboelectric effect. Even sulfur (40% of ebonite) has a higher electronegativity than e.g. carbon and hydrogen that are abundant in the fur which is why fur loses electrons and becomes positively charged.
Of course, the actual arrangement of the atoms in the molecules matters, too. So this overview of the periodic table was just an analogy, not a reliable way to find out the results of the triboelectric effect.
The following is multiple choice question (with options) to answer.
When a fluorine atom gains an electron, it becomes a negative what? | [
"fluoride ion",
"hydrogen ion",
"potassium ion",
"sulfide ion"
] | A | When a fluorine atom gains an electron, it becomes a negative fluoride ion. |
SciQ | SciQ-2114 | endocrinology, glucose, homeostasis, insulin, hypothalamus
Title: Role of the Hypothalmus in the control of Blood Sugar In homeostatic regulation of blood glucose, the receptor and effector is the Pancreas, but how does the control centre — the Hypothalamus — connect and link into this process? Your question doesn’t make it clear whether you think that the pancreas must be under the control of the hypothalmus, or whether you are asking whether it has an influence on the pancreas in relation to the secretion of insulin and glucagon, which control the concentration of blood glucose.
First, it has been long known that secretion of insulin can be influenced by the concentration of glucose in isolated pancreatic islets in vitro, so it can not be true that the effects must involve the hypothalmus. This is implicit in most book or general information articles you might find on the web, but for an original reference a review by W.J. Malaisse in Diabetologia 9, 167–173 (1973) seems highly cited.
I know almost nothing about physiology, but on searching the web for the role of the hypothalmus in glucose homeostasis, found a most readable prize-winning postgraduate essay on the topic by Syed Hussein of Imperial College London. I trust that it is in order to append an edited extract of this:
The following is multiple choice question (with options) to answer.
The endocrine system consists of cells, tissues, and organs that secrete what critical to homeostasis? | [
"saliva",
"hormones",
"acids",
"antibodies"
] | B | CHAPTER REVIEW 17.1 An Overview of the Endocrine System The endocrine system consists of cells, tissues, and organs that secrete hormones critical to homeostasis. The body coordinates its functions through two major types of communication: neural and endocrine. Neural communication includes both electrical and chemical signaling between neurons and target cells. Endocrine communication involves chemical signaling via the release of hormones into the extracellular fluid. From there, hormones diffuse into the bloodstream and may travel to distant body regions, where they elicit a response in target cells. Endocrine glands are ductless glands that secrete hormones. Many organs of the body with other primary functions—such as the heart, stomach, and kidneys—also have hormone-secreting cells. |
SciQ | SciQ-2115 | biochemistry, dna, structural-biology, 3d-structure
Note that although I only mention DNA above, papers discussing parallel RNA double helices in the same spirit would also be welcome.
Related question: why is DNA antiparallel? Can it be parallel? Surprisingly, a parallel DNA duplex has been reported! In a paper, Tchurikov et al have reported the presence of parallel complementary DNA in the non-coding region of alcohol dehydrogenase gene as well as between two Drosophila DNA sequences. The region, which is ~40 bp long, has 76% bases in same polarity along with complementarity. However, its presence in vivo and its significance are not known (they observed its existwnce in vitro).
Tchurikov et al, in another paper, have reported that parallel complementary RNA in E. coli plays some role in RNA interference and is indeed more effective than antisense RNA in silencing mRNA for gene expression regulation. They also propose the presence of such a system in vivo in E. coli cells. (Seemingly, this paper alone is enough to answer your question since it fulfills all your criteria).
In another paper, Szabat et al have shown that DNA, 2'-O-MeRNA and RNA oligonucleotides can adopt parallel duplex configuration at pH 5 and lower. Also, presence of LNA stabilizes parallel duplex configuration. This might seem helpful in processes such as RNA interference, though this study too was in vitro (obviously, in vivo LNA is not known).
Many such papers, like Westhof et al, Mohammadi et al, etc. have reported the presence of parallel duplex DNA.
References:
1. Tchurikov NA, Chernov BK, Golova YB, Nechipurenko YD. Parallel DNA: generation of a duplex between two Drosophila sequences in vitro. FEBS letters. 1989;257(2):415–8. pmid:2479581
2. Tchurikov, N. A., L. G. Chistyakova, G. B. Zavilgelsky, I. V. Manukhov, B. K. Chernov, and Y. B. Golova. 2000. Gene-specific silencing by expression of parallel complementary RNA in Escherichia coli. J. Biol. Chem. 275:26523–26529
The following is multiple choice question (with options) to answer.
What is formed when two dna strands link together in an antiparallel direction and are twisted? | [
"guanine",
"RNA",
"anti-helix",
"double helix"
] | D | Two DNA strands link together in an antiparallel direction and are twisted to form a double helix. The nitrogenous bases face the inside of the helix. Guanine is always opposite cytosine, and adenine is always opposite thymine. |
SciQ | SciQ-2116 | forces, pressure, fluid-statics, air, gas
I hop this description is clear enough, if not, feel free to ask for an explanation.
EDIT: Alright, I think I have understood it now. So the vacuum fills up because gas molecules move "randomly" around all the time and bump into each other. If there is a vacuum somewhere, they can freely move into there because there is nothing to bump against, so a lot of them end up in there, causing the pressure to equalize, because when it is, the molecules continue bumping around but do not "favour" a certain direction because there is less resistance there anymore.
Wind exists, because of course when many molecules have moved a certain direction, there are less of them where they used to be, which again is a lower-pressure area so it also fills up. This happens untill everything is mostly calm again.
Also, does this mean that pressure is the sum of the forces acting on the walls by the molecules randomly hitting the walls?
Is this correct? 'Pressure' of a gas is generated because of the collisions between gas molecules-gas molecules or gas molecules-wall of the container. Unless they collide, gas molucules move in straight lines with uniform velocity, which requires no external force (The impulsive forces act at the collisions are internal forces to the system).
If you put some gas molecules into a bottle, they spread throughout the bottle because there are no barriers inside the bottle. But they cannot go through the wall of the bottle. If you open the lid of the bottle, some of them come out to equalize the pressure inside and outside, because they like to minimize the number of collisions between them [ peace-loving :) ]. That is simply called they move due to pressure difference. But the real reason is you removed the barrier which prevented them from moving freely.
Imagine this way, you are running along a straight line and you see a door closed, so you turn back and again run. Next time you come and the door is opened so you freely move through the opened door. Did any force act on you? No.
In your example, the air is moving to the vacuum simply abolishing the pressure difference (This is explained in more details above) with uniform velocity. Therefore no force acts on the air. Thus no counter-force!
The following is multiple choice question (with options) to answer.
Particles of a gas are constantly moving and bumping into things. this gives gases what? | [
"velocity",
"resistance",
"pressure",
"strength"
] | C | Particles of a gas are constantly moving and bumping into things. This gives gases pressure. |
SciQ | SciQ-2117 | homework, plant-physiology, plant-anatomy
and 'Vascular Plants = Winning! - Crash Course Biology #37'
https://youtu.be/h9oDTMXM7M8?t=373
[5] Osmosis (water compensating solutes) "In Da Club - Membranes & Transport: Crash Course Biology #5"
https://youtu.be/dPKvHrD1eS4?list=PL3EED4C1D684D3ADF&t=148
Ian (and dad <= all errors and approximations are his :) ).
The following is multiple choice question (with options) to answer.
Which part of a leaf contains openings known as stomata, through which the exchange of gases takes place? | [
"cuticle",
"stoma",
"epidermis",
"phloem"
] | C | Which layers of the stem are made of parenchyma cells? a. cortex and pith b. phloem c. sclerenchyma d. xylem Like the rest of the plant, the stem has three tissue systems: dermal, vascular, and ground tissue. Each is distinguished by characteristic cell types that perform specific tasks necessary for the plant’s growth and survival. Dermal Tissue The dermal tissue of the stem consists primarily of epidermis, a single layer of cells covering and protecting the underlying tissue. Woody plants have a tough, waterproof outer layer of cork cells commonly known as bark, which further protects the plant from damage. Epidermal cells are the most numerous and least differentiated of the cells in the epidermis. The epidermis of a leaf also contains openings known as stomata, through which the exchange of gases takes place (Figure 30.8). Two cells, known as guard cells, surround each leaf stoma, controlling its opening and closing and thus regulating the uptake of carbon dioxide and the release of oxygen and water vapor. Trichomes are hair-like structures on the epidermal surface. They help to reduce transpiration (the loss of water by aboveground plant parts), increase solar reflectance, and store compounds that defend the leaves against predation by herbivores. |
SciQ | SciQ-2118 | homework, cell-membrane, human-physiology, lungs
Title: How many cell membranes are oxygen and carbon dioxide diffuse through in the lungs? In the lungs, oxygen and carbon dioxide pass through cell membranes by diffusion.
Which row is correct?
The correct answer is D, but I think it should be B. I can only think about three layers as maximum which are; epithelium of alveolus, endothelium of capillaries and the membrane of red blood cell. I don't know what are remainings.
Any help would be much appreciated! Oxigen goes from the alveolar's lumen to the cytoplasm of the erythrocyte, and that's 5 membranes:
the "top" of the alveolar epithelial cell
the "bottom" of such cell
the "top" of the endothelial cell (capillary)
the "bottom" of such cell
the erythrocyte membrane
You got all the cells right, but your only problem was this: oxygen diffuses through the cell membrane entering the cell, moves through the cytoplasm, and diffuses through the membrane again exiting the cell. So, for each cell, you have to count 2 membranes. For the last one, the erythrocyte, you have only 1 membrane (because it is $\ce{O2}$ final destination).
For the $\ce{CO2}$ the situation is a little bit more tricky. We have the same 4 membranes (2x epithelial cell and 2x capillary), but $\ce{CO2}$ can come from 2 locations:
from the erythrocyte, where it is formed from $\ce{H2CO3}$ (by the reaction $\ce{H2CO3 -> H2O + CO2}$) or released from the N-terminal group of proteins, like haemoglobin (where it has previously bound)
from the plasma (around 9% of the $\ce{CO2}$).
In the first case we have 5 membranes, and in the second case just 4.
So, the correct answer is D.
The following is multiple choice question (with options) to answer.
Which system transports oxygens to cells? | [
"vascular system",
"oxy system",
"circulatory system",
"nervous system"
] | C | An important function of the circulatory system is transporting oxygen to cells. |
SciQ | SciQ-2119 | biochemistry, botany, plant-physiology, photosynthesis
What are typical characteristics of different plants in this regard? I.e., how do common species of plants manage their C consumption before (and after) the development of leaves? There are quite a few questions and thoughts in there, I'll try to cover them all:
First, to correct your initial word equation: During photosynthesis, a plant translates CO2 and water into O2 and carbon compounds using energy from light (photons).
You are correct to assume the C is further used for the growing process; it is used to make sugars which store energy in their bonds. That energy is then released when required to power other reactions, which is how a plant lives and grows. C is also incorporated into all the organic molecules in the plant.
Plants require several things to live: CO2, light, water and minerals. If any of those things is missing for a sustained period, growth will suffer. Most molecules in a plant require some carbon, which comes originally from CO2, and also an assortment of other elements which come from the mineral nutrients in the soil. So the plant is completely reliant on minerals.
Most plants, before a leaf is established or roots develop, grow using energy and nutrients stored in the endosperm and cotyledons of the seed. I whipped up a rough diagram below. Cotyledons are primitive leaves inside the seed. The endosperm is a starchy tissue used only for storage of nutrients and energy. The radicle is the juvenile root. The embryo is the baby plant.
The following is multiple choice question (with options) to answer.
What is the part of a plant whose primary role is to collect sunlight and make food by photosynthesis? | [
"stems",
"seeds",
"roots",
"leaves"
] | D | Leaves are the keys not only to plant life but to all terrestrial life. The primary role of leaves is to collect sunlight and make food by photosynthesis. Despite the fundamental importance of the work they do, there is great diversity in the leaves of plants. However, given the diversity of habitats in which plants live, it’s not surprising that there is no single best way to collect solar energy for photosynthesis. |
SciQ | SciQ-2120 | redox
Title: Is it possible to write a redox reaction with two oxidations and one reduction together? Let's take the Redox reaction between ${MnO_4}^-, {C_2O_4}^{2-}$ and ${SO_3}^{2-} $
Is it possible to write the complete reaction as below or do I need to consider the two reactions separately?
$\ce{4MnO4- + 5C2O4^{2-} + 5SO3^{2-} -> 4Mn^2+ + 10CO2 + 5SO4^{2-}}$ I wouldn't try to combine these reactions. You would want to consider both reactions and maybe look up the standard reduction potentials of all reactants and products involved to give yourself an idea of what is oxidizing what and what is reducing what. In general, you should let the SRP's be a guide for trying to figure out what actually happens in these reactions.
The reaction you wrote doesn't really describe anything chemically. We have to make sure not only the math works out, but also the chemistry. Also, your charge balance is wrong, so even if the chemistry did work out, the reaction would be impossible. You seem to have 24 (-) on the reactants side and net 2 (+) on the products side.
Remember to always check BOTH your mass (MB) and charge balance (CB) work out when you're doing REDOX problems.
The following two reactions are the acidic balanced REDOX reactions for the the species you have written. Of course, these may not actually be the real reactions that would occur. For that, you would have to look things up in tables in your book.
$\ce{6 H+ + 2MnO4- + 5SO3^2- -> 5SO4^2- + 2Mn^2+ + 3H2O} \quad\text{(CB: -6 : -6)}$
$\ce{16 H+ + 2 MnO4- + 5C2O4^2- -> 10 CO2 + 2Mn^2+ + 8 H2O} \quad\text{(CB +4 : +4)}$
The following is multiple choice question (with options) to answer.
Technically, any redox reaction can be set up to make a what? | [
"skaht cell",
"Black Cell",
"voltaic cell",
"blocky cell"
] | C | Technically, any redox reaction can be set up to make a voltaic cell. In modern society, however, only certain redox reactions are put to practical use. A portable voltaic cell that generates electricity to power devices for our convenience is called a battery. All batteries are based on redox reactions. The first battery (called a “voltaic pile”) was constructed by the Italian scientist Alessandro Volta in 1800 and was based on the copper/zinc reaction depicted in - ball-ch14_s03_f01. Unfortunately, it was messy, requiring quantities of copper and zinc salts dissolved in water. In 1866, the French scientist Georges Leclanché invented the dry cell, a precursor to today’s modern battery. A schematic of a dry cell is shown in - ball-ch14_s03_f02. The zinc case and the central carbon rod serve as the anode and cathode, respectively. The other reactants are combined into a moist paste that minimizes free liquid, so the battery is less messy (hence the name dry cell). The actual redox reaction is complex but can be represented by the following redox reaction: + 2+ Zn + 2MnO2 + 2NH4 → Zn + Mn2O3 + 2NH3 + H2O A dry cell has a voltage of about 1.56 V. While common and useful, dry cells have relatively short lifetimes and contain acidic components. They also cannot be recharged, so they are one-use only. Batteries that can be used only once are calledprimary batteries. Figure 14.2 Dry Cells. |
SciQ | SciQ-2121 | evolution, species, speciation
Title: Are there any half-evolved animals alive today? I know that there are animals that are "simpler" than other animals but are there any that are half-evolved? Are there any animals with half-evolved functions, like arms, legs, etc?
This was part of the original question, but it was incorrect.
Saying that every species on the planet is "transitional" is an unacceptable answer because it only works on the assumption that macro-evolution is true.
Saying that all the transitional animals just died off also doesn't seem quite right. If all the previous transitional animals just went extinct, then wouldn't we just have a few specialized species alive today? This wouldn't allow for the diversity we see today.
I know that there are animals that are "simpler" than other animals but are there any that are half-evolved? Why aren't there living half ape and half humans?
Oh come on. You know if Australopithecines or Homo habilis still existed you would be asking "Why aren't there living half Homo habilis and half humans"? And when the other Great Apes go extinct you'll be wondering why there are no transitional forms between humans and monkeys. The answer to that question is, humans are apes; chimpanzees and we are pretty much as close as two species can be; we could have closer forms that survived but we could also have a much bigger gap between us and our closest relatives than we currently do. In other words, any ape is a valid example of something "half-human half-ape". It's like asking for a vehicle that's half-car, half-volvo.
Are there animals that are just starting to evolve arms and legs?
You mean, modifying fins into limbs in a general movement from water-living to land-living, like the first tetrapods are thought to have done? I like mudskippers.
Saying that every species on the planet is "transitional" because there are no ultimate or final species is an unacceptable answer because it only works on the assumption that macro-evolution is true.
The following is multiple choice question (with options) to answer.
What percentage of all species that ever lived on earth have gone extinct? | [
"99%",
"93 %",
"50%",
"25%"
] | A | Over 99 percent of all species that ever lived on Earth have gone extinct. Five mass extinctions are recorded in the fossil record. They were caused by major geologic and climatic events. Evidence shows that a sixth mass extinction is occurring now. Unlike previous mass extinctions, the sixth extinction is due to human actions. |
SciQ | SciQ-2122 | fluid-dynamics, diffusion, stochastic-processes
Title: How does dye move in water? My understanding is that dye moves through water primarily through diffusion. The introduction to these lecture notes seems to confirm:
If you we put a drop of red dye in water, it will slowly diffuse
throughout the water. Why does this happen? How fast does it happen?
What is going on microscopically? The microscopic mechanism of
diffusion is very simple: the dye molecules start densely concentrated
near one point. Then they get bumped by neighboring molecules until
they are spread out all over.
But later, the note do a short computation and conclude the following:
For example, taking a dye molecule in water with D = $10^{−9}
\frac{m^2}{s}$, to move $1$ $m$ would take $31$ years. So clearly
diffusion is not the main mechanism by which dyes move around in
water.
My intuition suggests that if I drop some dye in a shallow vat of water with $1$ $m$ radius, then the dye will saturate the water and hit the sides in far less than 31 years. If diffusion does not cause this, what does?
If diffusion does not cause this, what does?
Diffusion IS an important phenomenon but in the situation you describe it's somewhat 'obscured' by other transport phenomena.
Fick's Second Law (see link) really only works when there's no convection currents at all, or no currents caused by air drafts.
At room temperature in a low viscosity fluid that is a big ask: smallish temperature differences cause small density variations and thus convection currents, which provide a much faster transport mode than pure diffusion.
Diffusion would be better observed in a carefully thermostated, draft-free medium, possibly thickened somewhat with glycerine (e.g.)... assuming you've got a lot of time on your hands!
The following is multiple choice question (with options) to answer.
What is the diffusion of water known as? | [
"electrolysis",
"evaporation",
"hemostasis",
"osmosis"
] | D | Osmosis is the special case of the diffusion of water. It's an important means of transport in cells because the fluid inside and outside cells is mostly water. Water can pass through the cell membrane by simple diffusion, but it can happen more quickly with the help of channel proteins. Water moves in or out of a cell by osmosis until its concentration is the same on both sides of the cell membrane. |
SciQ | SciQ-2123 | thermodynamics, evaporation, gas, liquid-state
On the water surface, knowing the temperature, we can estimate the vapor pressure and vapor mixture fraction. Then there will be an diffusion process for the water vapor to move out and for the ambient air to move in. Because the water surface doesn't allow the air to further move, a circulation forms. When the water vapor moves out, the water vapor pressure drops, so more liquid water evaporates to fill up the loss of water vapor. The evaporation associates latent heat so water surface area temperature drops (you may see dew on the bowl wall). Then a heat transfer process starts which may initiate water circulation as well.
As this is complex, doing test might be a quick way to get the K value if you assume it is a constant, which is questionable.
The following is multiple choice question (with options) to answer.
What is it called when plants release water vapor through their leaves? | [
"photosynthesis",
"evaporation",
"transpiration",
"eutrophication"
] | C | Transpiration is like evaporation because it changes liquid water to water vapor. In transpiration, plants release water vapor through their leaves ( Figure below ). This water vapor rises into the atmosphere. |
SciQ | SciQ-2124 | the-moon, the-sun, earth
That explains the circular movement of the stars, the Sun and the Moon.
This is true for all locations on the Earth, except for the equator:
Is the Earth spinning? That depends, you can always choose a frame of reference that suits you. However, only one of them are non-rotating, the Inertial frame. In all the others we have fictitious forces acting, like centrifugal or Coriolis forces.
We can test if the Earth rotates by watching a pendulum throughout a day. The pendulum would then seem to slowly rotate during this period of time, meaning some fictitious "force" is acting on it. That means that we are located in a rotating frame of reference, and thus the Earth rotates.
The following is multiple choice question (with options) to answer.
Earth goes through regular changes in its position relative to? | [
"the moon",
"the sun",
"mars",
"saturn"
] | B | Earth goes through regular changes in its position relative to the Sun. Its orbit changes slightly. Earth also wobbles on its axis of rotation. The planet also changes the tilt on its axis. These changes can affect Earth’s temperature. |
SciQ | SciQ-2125 | physical-chemistry, electrochemistry, conductivity
$$t_\circ^- = \frac{\Lambda_\mathrm{m}^\circ(\ce{B-})}{\Lambda_\mathrm{m}^\circ(\ce{A+})+\Lambda_\mathrm{m}^\circ(\ce{B-})}$$
(here $t_\circ^i$ designates a limiting transport number ie one in the limit of dilute electrolyte solution).
In the early days of the study of electrolytes, Hittorf developed a way of determining the ratio of transport numbers by measuring the concentrations of electrolytes in different parts of an electrolytic cell. Say the cell contains a cathode, an anode, and a bridging chamber. Cations are attracted toward the cathode chamber and depleted at the cathode, and anions are similarly depleted at the anode but also migrate into the anode chamber. The change in the concentration of cations in the cathode chamber is therefore proportional to the current at the electrode minus the fraction of current carried by cations replenishing the cation chamber:
$$\begin{align} \frac{dc_+}{dt} &= \frac{I_+}{z_+F} - \frac{I}{z_+F} \\ &= \frac{(t_+-1)I}{z_+F} \\ &= \frac{-t_-I}{z_+F} \end{align}$$
A similar equation can be written for the anions. The resulting concentrations in the chambers can be related to the migration rates $v_i$ of the ions , which can in turn be related to the transport numbers as
$$\frac{t^+}{t^-} = \frac{|Z^+v^+|}{|Z^+v^-|}$$
Therefore from measurement of electrolyte concentrations in different parts of a cell it is possible to deduce the relative molar conductivities of the components of an electrolyte.
The following is multiple choice question (with options) to answer.
A symporter carries how many different molecules or ions in the same direction? | [
"two",
"three",
"four",
"one"
] | A | Figure 5.17 A uniporter carries one molecule or ion. A symporter carries two different molecules or ions, both in the same direction. An antiporter also carries two different molecules or ions, but in different directions. (credit: modification of work by “Lupask”/Wikimedia Commons). |
SciQ | SciQ-2126 | biochemistry
Specific Force Deficit in Skeletal Muscles of Old Rats Is Partially
Explained by the Existence of Denervated Muscle Fibers
Association of adiponectin and resistin with adipose tissue
compartments, insulin resistance and dyslipidaemia
Shifts in the Distribution of Mass Densities Is a Signature of
Caloric Restriction in Caenorhabditis elegans
The following is multiple choice question (with options) to answer.
Large amounts of fuel are stored in skeletal muscles, adipose tissues and what organ? | [
"liver",
"skin",
"spleen",
"kidney"
] | A | |
SciQ | SciQ-2127 | geophysics, earth-history
Title: Impact Erosion Selectivity In Offloading Radioactive Material ref : https://science.ubc.ca/news/asteroid-impact-erosion-helped-make-earth-habitable
According to the theory of impact erosion, the early crust was presumably much hotter w/ radioactive isotopes (U & K, primarily) and thus less congenial for the later development of life. Asteroid bombardment - I suppose during the late heavy bombardment - then blew off a sufficient chunk of this material to lower net radioactivity in the crust.
Was this simply because beforehand for some reason there was an upward gradient of radioactivity in the primeval crust ? I'm at a loss to conceive a selective mechanism for this phenomenon. Any paleo-geologists in the house ? All the original research paper is saying is that there might be less radioactive elements in the silicate Earth (crust + mantle) than previously thought. And if there had been more of those elements, there would have been more internal heat, thus a different tectonic regime, a different volcanism, a different geodynamo, a different atmosphere... And maybe, maybe, these different conditions would have prevented the emergence of life.
Also, don't forget that even is uranium is dense, it doesn't "sink below the crust". The mantle is solid rock, uranium is trapped in the crystal lattice of minerals, but it is an incompatible element, meaning it will preferentially go into the melt when the mantle partially melt. These melts then rise by buoyancy and actually make the bulk of the continental crust. So it makes perfect sense that the crust is uranium-enriched and the mantle uranium-depleted. Then, if you remove some of this crust after its formation, you will indeed remove some radioactive elements compared to the original composition (I'm not saying it happened, but the model is perfectly logical).
The following is multiple choice question (with options) to answer.
Intrusive igneous rocks cool from magma slowly in the crust and have large what? | [
"atoms",
"pores",
"crystals",
"coal deposits"
] | C | Intrusive igneous rocks cool from magma slowly in the crust. They have large crystals. |
SciQ | SciQ-2128 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
What is the term used for the ability of salamanders to grow back lost limbs and other body parts? | [
"expansion",
"extraction",
"regeneration",
"transformation"
] | C | Salamanders are carnivorous , eating only other animals, not plants. They will eat almost any smaller animal, such as worms, centipedes, crickets, spiders, and slugs. Some will even eat small invertebrates. Finally, salamanders have the ability to grow back lost limbs, as well as other body parts. This process is known as regeneration. |
SciQ | SciQ-2129 | meteorology, snow, radar
Also note that winter precipitation adds an extra complication because the particles are lighter in weight and can thus be blown about more by vertical and horizontal winds. Raindrops (and hail) are quite likely to fall unless extreme updrafts exist because they are heavy. But drizzle, snow, and sleet may be blown around quite a bit. Without a time-intensive dual-Doppler analysis, you cannot know the wind motion in the storm thoroughly, and therefore will have varying results at times.
And finally, the big wrench is unfortunate inherent to how radars work. They measure the percentage of their sent energy that is reflected back to them. That's great because that's directly connected to the diameter of the item falling (to the 6th power). But unfortunately the grand problem is that in a storm, there is a huge variety of drop/flake sizes mixed together at once... such that we can't extract which combination of particle sizes created it (and thus can't calculate volume to actually know the rain/snow amount that falls). It could be like 6 medium size flakes causing the 10 dBZ echo... or 2 large flakes and 10 small flakes... and each combination is a different volume/snow total. (to see the nitty-gritty math details on this, read more here.) So we can never know for sure the exact rain/snow falling using just radar. The good news is we've at least done lots of experiments and come up with some fairly useful best-practice formulas for using the Z-R ratio in different scenarios. Good, but not perfect.
The following is multiple choice question (with options) to answer.
A winter storm is called what? | [
"blizzard",
"snow storm",
"tempest",
"gale"
] | A | A storm is an episode of severe weather caused by a major disturbance in the atmosphere. Storms can vary a lot in the time they last and in how severe they are. A storm may last for less than an hour or for more than a week. It may affect just a few square kilometers or thousands. Some storms are harmless and some are disastrous. The size and strength of a storm depends on the amount of energy in the atmosphere. Greater differences in temperature and air pressure produce stronger storms. Types of storms include thunderstorms, tornadoes, hurricanes, and winter storms such as blizzards. |
SciQ | SciQ-2130 | zoology, terminology, nomenclature, invertebrates, etymology
Urochorda
Cephalochorda
Craniata
which is more or less the accepted division today, with Urochorda being called Urochordata now.
In this essay, Lankester says:
The evidence of degeneration is admitted as conclusive in the case of the parasitic Crustacea and Cirrhipedes. It is equally incontestable in that very large and varied group of non-parasitic organisms, the Tunicata (Urochordate Vertebrata).2
(in the above 'Vertebrata' is what we call 'Chordata'). He adds this footnote:
2The whole argument as to the Tunicates of course rests on the view- supported by many arguments, that the larval urochord, which many of
them possess, is not a larval organ acquired by larval adaptation, but is hereditary and transmitted from adult ancestors.
The term 'urochord' seems to be established and used without comment there, and probably is taken as simple neo-Latin for 'tail chord', although that may be somewhat loose, perhaps meaning the notochord is present but does not extend into the head. A 1913 Webster's Dictionary defines urochord as:
(Zool.) The central axis or cord in the tail of larval ascidians and of certain adult tunicates.
In 1882, Lankester futher discussed the anatomy of the tunicates in the context of the division of the chordata in a paper called "The Vertebration of the Tail of Appendiculariæ". This paper includes an illustration of a larval tunicate with the "notochord (urochord)" indicated.
The following is multiple choice question (with options) to answer.
The trochophre, a unique larval form, is found in the life cycle of which animal classification. | [
"mollusks",
"eels",
"sharks",
"coral"
] | A | Mollusks reproduce sexually. Most species have separate male and female sexes. Gametes are released into the mantle cavity. Fertilization may be internal or external, depending on the species. Fertilized eggs develop into larvae. There may be one or more larval stages. Each one is different from the adult stage. Mollusks (and annelids) have a unique larval form called a trochophore. It is a tiny organism with cilia for swimming. |
SciQ | SciQ-2131 | ## Ch112
The aorta carries blood away from the heart at a speed of about 39 cm/s and has a radius of approximately 1.0 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.072 cm/s, and the radius is about 6.2 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
• solve in the same approach...
The aorta carries blood away from the heart at a speed of about 44 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.071 cm/s, and the radius is about 6.4 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Solution:
The volume has to be the same, so:
44cm/s * 1.44pi cm^2 = 199.05 cm^3/s
so x(.071cm/s * pi*.00064^2) = 199.05cm^3/s
x = (44 * 1.44pi)/(.071 * pi * .00064^2) = 2.17869718 * 10^9 capillaries
• The aorta carries blood away from the heart at a speed of about 37 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.069 cm/s, and the radius is about 6.3 x 10^-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Flow rate = Cross sectional area * speed
Blood flow from the aorta = (pi)(1.2)^2(37) = 167.38 cm^3/sec.
The following is multiple choice question (with options) to answer.
Within organs, arteries branch into what small vessels that convey blood to the capillaries? | [
"blood valves",
"aeortic vessels",
"arterioles",
"Metarterioles"
] | C | |
SciQ | SciQ-2132 | physical-chemistry, nanoscience
Title: What Makes Diamonds Difficult to Produce? Having seen an answer over on Worldbuilding about very strong/dense wood that suggested artificially creating some enzymes that would manufacture diamond/graphene as the cellular binding materials in the tree, I said to myself, "Hold on, I know this won't work: creating diamonds requires high temperature and/or pressures...doesn't it?"
But I was unable to locate any information as to why this is the case: that is, what physical property of the bonds or arrangement of the carbon atoms dictates the intense pressures needed to cause the formation of the crystal lattice? Or is there really nothing standing in the way of a chemical process (i.e. an enzyme constructing it a few atoms at a time, albeit with large energy expenditures and slow timescales) that would do it other than "we don't know how to make that."
The covenant bond energy between two carbon atoms seems pretty high, I'll admit, at 348 kJ/mol, but it's less than some other bonds, say Carbon and Hydrogen at 419 kJ/mol (source). So it doesn't seem like that's the limiting factor. I do know that there is energy stored in the organization of the lattice itself, but I don't know how much that contributes; Wikipedia only helpfully notes that the energy is "greater in materials like diamond than sugar."
The following is multiple choice question (with options) to answer.
Diamond is extremely hard because of the strong bonding between ______ in all directions? | [
"consistent atoms",
"liquid atoms",
"hydrogen atoms",
"carbon atoms"
] | D | Figure 10.43 Diamond is extremely hard because of the strong bonding between carbon atoms in all directions. Graphite (in pencil lead) rubs off onto paper due to the weak attractions between the carbon layers. An image of a graphite surface shows the distance between the centers of adjacent carbon atoms. (credit left photo: modification of work by Steve Jurvetson; credit middle photo: modification of work by United States Geological Survey) You may be less familiar with a recently discovered form of carbon: graphene. Graphene was first isolated in 2004 by using tape to peel off thinner and thinner layers from graphite. It is essentially a single sheet (one atom thick) of graphite. Graphene, illustrated in Figure 10.44, is not only strong and lightweight, but it is also an excellent conductor of electricity and heat. These properties may prove very useful in a wide range of applications, such as vastly improved computer chips and circuits, better batteries and solar cells, and stronger and lighter structural materials. The 2010 Nobel Prize in Physics was awarded to Andre Geim and Konstantin Novoselov for their pioneering work with graphene. |
SciQ | SciQ-2133 | ichthyology, vertebrates
Title: If an organism is supported only by cartilage, does it have an endoskeleton? Lamprey and sharks lack bones, but does this mean they are not classified as having an endoskelton? Does an organism need bone to be considered as having an endoskeleton? From wikipedia
An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.
Cartilage is a mineralized tissue so it counts as a skeleton from this definition. A bit further in the wikipedia article it says
The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage)
The following is multiple choice question (with options) to answer.
Vertebrates. from the smallest of fish to us. one of the main features we all have in common is our what? | [
"laying eggs",
"backbone",
"hair",
"warm blood"
] | B | Vertebrates. From the smallest of fish to us. One of the main features we all have in common is our backbone. Vertebrates describes main biological features of fish, amphibians, reptiles, birds, and mammals. |
SciQ | SciQ-2134 | eyes
To directly answer your question - yes, I believe this is primarily the "fault" of the eye, rather than the brain. The brain has a role in identifying the flicker at a subconscious level, in terms of fight or flight response, but the eye is responsible for providing the elevated sensitivity at the peripheral.
The following is multiple choice question (with options) to answer.
The fight or flight response and similar responses are controlled by what part of the nervous system? | [
"autonomous",
"cells",
"spinal cord",
"central nervous system"
] | A | Image copyright CREATISTA, 2014. The autonomous nervous system controls responses such as fight or flight . Used under license from Shutterstock. com. |
SciQ | SciQ-2135 | thermodynamics
Title: Gas in movement Suppose I have a gas contained in a solid box and I drop it from a certain height, is the temperature of the gas going to change because of the velocity that it acquires during the fall? If so, by how much? The temperature of the gas will go up, but only after the box hits the ground and the falling gas swirls around and randomizes its velocity. The lost potential energy of the gas has to show up somewhere...
The following is multiple choice question (with options) to answer.
Deposition refers to when a gas changes to what state? | [
"solid",
"half liquid half gas",
"plasma",
"liquid"
] | A | Deposition is the change of state from a gas to a solid. |
SciQ | SciQ-2136 | nuclear-physics, mass-energy
Title: Why does mass change in to energy during a nuclear change? I have been doing some research on nuclear changes and I have found that the energy released during a nuclear change comes from a minuscule amount of mass that is converted in to energy. After making some more research it seemed completely logical because of Einstein’s famous energy equation, but I was left with a couple of questions roaming my mind.
The following is multiple choice question (with options) to answer.
Nuclear changes occur with a simultaneous release of what, and a slight drop in mass? | [
"mineral",
"oil",
"energy",
"hydrogen"
] | C | Nuclear changes occur with a simultaneous release of energy. Where does this energy come from? If we could precisely measure the masses of the reactants and the products of a nuclear reaction, we would notice that the amount of mass drops slightly in the conversion from reactants to products. Consider the following nuclear reaction, in which the molar mass of each species is indicated to four decimal places:. |
SciQ | SciQ-2137 | training, ai-design
Reward modelling is more interesting, and it is relate to reinforcement learning. Unlike in classic deep learning, which focus mainly in the design of loss functions, in reinforcement learning the main component is the reward function. A reward function is much trickier to design compare to a loss function, cause it's usually impossible to predict all possible non useful strategies that an agent might learn (e.g. running in circles to prevent to hit obstacles). So, to compensate for this difficulties, some people came up with the idea of letting artificial agents to design their own reward function, with the only constrain of an external human annotator penalizing dumb functions that emerge during the process. It's a bit hard to explain the idea shortly, but I personally find it really fascinating, and I suggest you also to take a look at this video for a more complete explanation.
The following is multiple choice question (with options) to answer.
The way of learning that involves reward and punishment is called? | [
"mixed",
"pressure",
"conditioning",
"foolish"
] | C | Conditioning is a way of learning that involves a reward or punishment. If you ever trained a dog to obey a command, you probably gave the dog a tasty treat each time he performed the desired behavior. It may not have been very long before the dog would reliably follow the command in order to get the treat. This is an example of conditioning that involves a reward. |
SciQ | SciQ-2138 | neuroscience, biophysics
Imagine the neuron like a circuit. We can imagine that the electro-chemical gradient for each ion species (Potassium, Sodium, and so on) as batteries. So When the ions flow according to their electrochemical gradient, the potassium current flows outward and sodium current flows inward as dictated by these batteries reversal potentials [negative for potassium, positive for sodium].
However, note that this will discharge those batteries, i.e. the concentration of sodium on the outside of the cell will drop (slightly) as sodium flows inward the cell, and potassium flows outward the concentration on the inside will drop slightly. Thus the magnitude of the reversal potential of the Sodium and Potassium drops (they move closer to zero).
To counteract this discharge the Sodium/Potassium pumps expends energy in the form of ATP in order to recharge the batteries. The amount of current that the pumps moves is very small relative to the larger currents of sodium rushing in and the potassium rushing out during an Action Potential. Thus when a neuron fires there is very little overall current contribution from the pumps.
When the neuron is at rest (not firing) then the Sodium/Potassium pump is able to recharge the membrane and the current becomes important. Still this is a very slow process, relative to action potentials.
Another thing to note, even though the cell is at rest the batteries are discharging slightly. Their is a leakiness to the membrane, sodium leaks in and potassium leaks out. Thus the pump's current will counteract these leaky currents at rest, keeping the batteries charged and thus the overall net current across the membrane at rest will be zero.
Remember though, these currents are very small currents.
EDIT: Based on Discussion with @Christiaan, I decided to post a update to clarify.
At rest potential Sodium Ion influx is much smaller than potassium ion efflux and thus can be ignored. Whether or not Sodium is ignored the above still holds true. The neuron's membrane is at rest which means the net current is equal to zero. This means that the outward potassium current is counterbalanced by the pump's current thus keeping the relative concentrations of Potassium and Sodium constant while at rest and maintaining a steady rest potential.
EDIT 2: Clarifying as per OP comment:
The following is multiple choice question (with options) to answer.
The sodium-potassium pump is an active transport pump that exchanges sodium ions for what? | [
"potassium ions",
"chlorine ions",
"oxygen ions",
"nitrogen ions"
] | A | The sodium-potassium pump is an active transport pump that exchanges sodium ions for potassium ions. |
SciQ | SciQ-2139 | newtonian-mechanics, forces, mass, velocity
Title: velocity, mass and force Is there an equation linking velocity, mass and force? I want to find the maximum force that an object of any given mass could exert. Assuming, the object with the given velocity stops dead in an instant, I thought of using F=ma but there is no time frame for the slowing down of the object since it's instant. Thank you Change in momentum $\Delta m v$ is equal to impulse $F \Delta t$, the force multiplied with the time that force acts on the body.
So to stop in an instant, the force is very large.
The following is multiple choice question (with options) to answer.
Mass multiplied by velocity equals what force? | [
"inertia",
"bounce",
"momentum",
"kinetic energy"
] | C | - Momentum equals mass multiplied by velocity. It is a vector, direction must be considered. Always define a positive direction and be consistent. |
SciQ | SciQ-2140 | evolution, human-evolution
Apes
The split between the line leading to modern humans and the line leading to modern chimpanzees occured somewhere around 4 to 7 million years ago. The clade is called Hominini. The split between those and the line leading to modern gorillas occured around 8 to 19 million years ago (yes, the dates are getting fuzzier). A fossil coming close to this ancestor may be Nakalipithecus nakayamai, however, we only have a fossil jaw from that species.
Going back, we get to the split between modern-day humans/chimpanzees/gorillas and modern-day orang-utans. This is the "ape" family, Hominidae. The largest ape that we know of, Gigantopithecus, that grew to about 3 meters, is classified as an orang-utan. Note that this is not a direct ancestor of humans. Even if our ancestors were larger than modern humans at this point it's unlikely that we are talking about anything larger than a big gorilla.
Primates
Going a bit in the reverse order here: The first true primates evolved around 55 million years ago. Fossils from that time are about the size of squirrels. Humans are "old world monkeys" who first appeared around 40 million years ago - the fossils from that clade we know, for example Apidium or Aegyptopithecus are a bit larger, some as large as a dog.
Primate-like mammals
The first primate-like mammals, called Plesiadapiformes appeared around 60 million years ago. We don't know all that much about them, but the most famous Purgatorius was the size of a rat or mouse.
Mammals / placenta mammals
Going back even further, things become even murkier, but early mammals were small. Placentalia, placental mammals appeared around 90 million years ago. They were small, arboreal (tree-dwelling) animals. Early mammals appeared around 160 million years ago and fossils we have from that time place them around the size of a shrew.
Now, is it possible that there were larger mammals in there somewhere, that then "shrunk" again? Sure. Just unlikely.
Therapsid
The following is multiple choice question (with options) to answer.
How many years ago did early amniotes diverge into two groups? | [
".416 million years",
".175 million years",
"20 million years",
"320 million years"
] | D | By about 320 million years ago, early amniotes had diverged into two groups, called synapsids and sauropsids. Synapsids were amniotes that eventually gave rise to mammals. Sauropsids were amniotes that evolved into reptiles, dinosaurs, and birds. The two groups of amniotes differed in their skulls. The earliest known reptile, pictured in Figure below , dates back about 315 million years. |
SciQ | SciQ-2141 | temperature, radiation, thermal-radiation, sun
Temperature [K] | Ratio | Ratio
| [10^(11) Hz] | [10^(13) Hz]
------------------------------------------------------
1.0000000 | 2.2 x 10^(8) | 5.1 x 10^(833)
10.000000 | 16.2 | 2.3 x 10^(83)
100.00000 | 5.5 | 2.2 x 10^(8)
1000.0000 | 5.0 | 16.2
10000.000 | 5.0 | 5.5
100000.00 | 5.0 | 5.0
If the temperature of the sun decreased N times, what would be the effect on the radiation intensity received on earth?
The following is multiple choice question (with options) to answer.
The intensity or rate of radiation emission _________ with temperature? | [
"randomly fluctuates",
"does not vary",
"increases",
"decreases"
] | C | Figure 29.3 Graphs of blackbody radiation (from an ideal radiator) at three different radiator temperatures. The intensity or rate of radiation emission increases dramatically with temperature, and the peak of the spectrum shifts toward the visible and ultraviolet parts of the spectrum. The shape of the spectrum cannot be described with classical physics. |
SciQ | SciQ-2142 | neuroscience, neurophysiology, memory, cognition
References
- Kuhl et al., Nature Neurosci (2007); 10: 908-14
- Shea & Right, Res Quarterly Exercise Sport (1991); 62(3)
- Stronks et al., Brain Res (2015); 1624: 140–52
The following is multiple choice question (with options) to answer.
For the most part, cognitive functions reside where? | [
"the heart",
"the limbic system",
"the spine",
"the cortex"
] | D | |
SciQ | SciQ-2143 | ## Ch112
The aorta carries blood away from the heart at a speed of about 39 cm/s and has a radius of approximately 1.0 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.072 cm/s, and the radius is about 6.2 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
• solve in the same approach...
The aorta carries blood away from the heart at a speed of about 44 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.071 cm/s, and the radius is about 6.4 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Solution:
The volume has to be the same, so:
44cm/s * 1.44pi cm^2 = 199.05 cm^3/s
so x(.071cm/s * pi*.00064^2) = 199.05cm^3/s
x = (44 * 1.44pi)/(.071 * pi * .00064^2) = 2.17869718 * 10^9 capillaries
• The aorta carries blood away from the heart at a speed of about 37 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.069 cm/s, and the radius is about 6.3 x 10^-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Flow rate = Cross sectional area * speed
Blood flow from the aorta = (pi)(1.2)^2(37) = 167.38 cm^3/sec.
The following is multiple choice question (with options) to answer.
What is the term for the force exerted by circulating blood on the walls of blood vessels? | [
"blood pressure",
"blood energy",
"circulation pressure",
"heart pressure"
] | A | The force exerted by circulating blood on the walls of blood vessels is called blood pressure . Blood pressure is highest in arteries and lowest in veins. When you have your blood pressure checked, it is the blood pressure in arteries that is measured. High blood pressure, or hypertension , is a serious health risk but can often be controlled with lifestyle changes or medication. You can learn more about hypertension by watching the animation at this link: http://www. healthcentral. com/high-blood-pressure/introduction-47-115. html . |
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